U.S. patent number 4,820,041 [Application Number 06/930,792] was granted by the patent office on 1989-04-11 for position sensing system for surveying and grading.
This patent grant is currently assigned to Agtek Development Co., Inc.. Invention is credited to Richard W. Davidson, John W. Fletcher.
United States Patent |
4,820,041 |
Davidson , et al. |
April 11, 1989 |
Position sensing system for surveying and grading
Abstract
A position sensing apparatus and method useful for surveying,
marking, and grading implement sensing and control is disclosed.
The position sensing apparatus includes two laser reference
stations, each of which projects a laser beam that periodically
sweeps in a plane across the area to be surveyed. Each time a laser
beam strikes the opposite reference station, a radio timing signal
is broadcast by that reference station. The position sensing
apparatus also includes a portable sensing station that comprises a
laser beam receiver, a radio reciever, and a programmed computer.
The planar position of the portable sensing station relative to the
reference stations is computed by a triangulation technique based
on the relative timing of detection of the laser beams by the laser
beam receiver and the reception of the radio timing signals by the
radio receiver. Elevation is determined according to the height at
which one of the laser beams strikes the laser beam receiver.
Inventors: |
Davidson; Richard W. (Dublin,
CA), Fletcher; John W. (Pleasanton, CA) |
Assignee: |
Agtek Development Co., Inc.
(Livermore, CA)
|
Family
ID: |
25459777 |
Appl.
No.: |
06/930,792 |
Filed: |
November 12, 1986 |
Current U.S.
Class: |
356/3.12;
172/4.5; 180/168; 33/293; 33/294; 33/296; 342/53; 342/54;
356/141.5; 356/3.09; 356/399; 356/4.08; 700/302; 701/50;
701/514 |
Current CPC
Class: |
E02F
3/842 (20130101); E02F 3/847 (20130101); E02F
9/2025 (20130101); G01C 15/004 (20130101); G01S
5/16 (20130101) |
Current International
Class: |
E02F
9/20 (20060101); E02F 3/76 (20060101); E02F
3/84 (20060101); G01C 15/00 (20060101); G01S
5/00 (20060101); G01S 5/16 (20060101); G01C
003/20 (); G01C 015/06 (); G01B 011/26 (); E02F
003/76 () |
Field of
Search: |
;356/1,5,141,152,9,15,17,146,399 ;33/293,294,296 ;172/4.5
;342/53,54 ;180/167,168 ;364/167,168,424,449,456 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buczinski; Stephen C.
Assistant Examiner: Wallace; Linda J.
Attorney, Agent or Firm: Limbach, Limbach & Sutton
Claims
What is claimed is:
1. A position sensing apparatus comprising:
a first energy beam transmitter operable for projecting a first
energy beam that sweeps in a plane across an area in which position
sensing is to occur;
first reference signal means for generating a first reference
signal when said first energy beam is aligned with a first
reference line;
a second energy beam transmitter operable for projecting a second
energy beam that sweeps in a plane across said area, wherein said
first and second energy beam transmitters are positioned apart;
second reference signal means for generating a second reference
signal when said second energy beam is aligned with a second
reference line;
an energy beam receiver operable for detecting said first and
second energy beams, wherein said energy beam receiver is placed at
a location at which the position is to be determined;
a reference signal receiver operable for receiving said first and
second reference signals; and
processing means coupled to said energy beam and reference signal
receivers and responsive to the timing of the detection of said
energy beams relative to the receipt of said reference signals for
determining the position of said energy beam receiver relative to
said reference lines and said energy beam transmitters.
2. An apparatus as recited in claim 1 wherein the orientations of
said reference lines and the positions of said energy beam
transmitters are known relative to an origin, and wherein said
processing means includes means for transforming the measured
position of said energy beam receiver relative to said reference
lines and said energy beam transmitters into a position relative to
said origin.
3. An apparatus as recited in claim 1 wherein said first and second
energy beams are laser beams, and wherein said energy beam receiver
includes detection means that are operable for detecting laser
light.
4. An apparatus as recited in claim 1 wherein said first energy
beam rotates in a first plane and said second energy beam rotates
in a second plane that is substantially parallel to and spaced
apart from said first plane.
5. An apparatus as recited in claim 4 wherein both said first and
second planes are substantially horizontal.
6. An apparatus as recited in claim 1 wherein said first energy
beam sweeps at a constant angular velocity, and wherein said
processing means includes means for determining the angle between
said first reference line and a line extending from said first
energy beam transmitter to said energy beam receiver according to
the ratio of the time interval between the detection of said first
energy beam by said energy beam receiver and the receipt of said
first reference signal by said reference signal receiver to the
time interval defined by the rotational period of said first energy
beam.
7. An apparatus as recited in claim 6 wherein said second energy
beam sweeps at a constant angular velocity, and wherein said
processing means includes means for determining the angle between
said second reference line and a line extending from said second
energy beam transmitter to said energy beam receiver according to
the ratio of the time interval between the detection of said second
energy beam by said energy beam receiver and the receipt of said
second reference signal by said reference signal receiver to the
time interval defined by the rotational period of said second
energy beam.
8. An apparatus as recited in claim 7 wherein said processing means
includes means for determining said rotational period of said first
energy beam according to the time period between the receipt of two
successive first reference signals, and for determining said
rotational period of said second energy beam according to the time
period between the receipt of two successive second reference
signals.
9. An apparatus as recited in claim 1 wherein said first reference
signal means includes a first energy beam detector for detecting
said first energy beam, and also includes first signalling means
responsive to said first energy beam detector for generating said
first reference signal upon detection of said first energy beam
during each rotation of said first energy beam, wherein said first
energy beam detector is positioned apart from said first energy
beam transmitter and the line therebetween defines said first
reference line.
10. An apparatus as recited in claim 9 wherein said second
reference signal means includes a second energy beam detector for
detecting said second energy beam, and also includes second
signalling means responsive to said second energy beam detector for
generating said second reference signal upon detection of said
second energy beam during each rotation of said first energy beam,
wherein said second energy beam detector is positioned apart from
said second energy beam transmitter and the line therebetween
defines said second reference line.
11. An apparatus as recited in claim 10 wherein said first energy
beam detector is coupled to and located with said second energy
beam transmitter, wherein said second energy beam detector is
coupled to and located with said first energy beam transmitter, and
wherein said first and second reference lines extend between said
first and second energy beam transmitters.
12. An apparatus as recited in claim 1 wherein said first reference
signal means is mounted on said second energy beam transmitter,
wherein said second reference signal means is mounted on said first
energy beam transmitter, whereby said first and second reference
lines extend between said first and second energy beam
transmitters.
13. An apparatus as recited in claim 1 wherein said first and
second reference signal means are mounted together at a position
separate from said first and second energy beam transmitters.
14. An apparatus as recited in claim 13 wherein said first and
second reference signal means are positioned between and aligned
with said first and second energy beam transmitters, whereby said
first and second reference lines extend between said first and
second energy beam transmitters.
15. An apparatus as recited in claim 1 wherein said first reference
signal means broadcasts said first reference signal as a radio
frequency signal, wherein said second reference signal means
broadcasts said second reference signal as another radio frequency
signal, and wherein said reference signal receiver includes a radio
receiver that is operable for receiving and distinguishing between
said radio frequency signals.
16. An apparatus as recited in claim 1 wherein one of said energy
beams is a datum beam that defines a datum plane, and wherein said
position sensing apparatus further comprises elevation measuring
means for determining the elevation of a location according to the
height at which said energy beam receiver detects said datum energy
beam.
17. An apparatus as recited in claim 16 wherein said datum plane is
substantially horizontal.
18. An apparatus as recited in claim 16 wherein said elevation
measuring means includes a support of adjustable length for
supporting said energy beam receiver and means for measuring the
extension of said support at which said energy beam receiver
detects said datum energy beam.
19. An apparatus as recited in claim 16 wherein said energy beam
receiver includes a linearly extending array of energy sensitive
receiving cells including a datum cell, wherein said linearly
extending array crosses said datum plane, and wherein said energy
beam receiver is properly positioned for height measurement when
said datum cell detects said datum energy beam.
20. An apparatus as recited in claim 19 wherein said energy beam
receiver includes indicator means for indicating whether receiving
cells above or below said datum cell are detecting said datum
energy beam, wherein the detection of said datum energy beam by a
receiving cell positioned above said datum cell indicates that said
energy beam receiver is positioned too low, and wherein the
detection of said datum energy beam by a receiving cell positioned
below said datum cell indicates that said energy beam receiver is
positioned too high.
21. An apparatus as recited in claim 1 further including a
plurality of energy beam receivers, each placed at a location at
which the position is to be determined and each coupled to said
processing means, wherein said processing means includes means for
determining the position of each of said energy beam receiver
relative to said reference lines and said energy beam
transmitters.
22. An apparatus as recited in claim 1 further comprising more than
two energy beam transmitters, each operable for striking said
energy beam receiver, and reference signal means associated with
each energy beam transmitter for generating a reference signal when
the associated energy beam is aligned with a corresponding
reference line, and wherein said processing means further includes
means responsive to all energy beams and reference signals for
determining the position of said energy beam receiver relative to
said reference lines and said energy beam transmitters.
23. A position sensing apparatus comprising:
a first laser beam transmitter operable for projecting a first
laser beam that rotates at a constant angular velocity in a first
plane, wherein said first plane defines a datum plane;
a second laser beam transmitter operable for projecting a second
laser beam that rotates at a constant angular velocity in a second
plane substantially parallel to said first plane, wherein said
first and second laser beam transmitters are positioned apart at
known locations;
a first laser beam detector mounted to said second laser beam
transmitter and operable for detecting when said first laser beam
strikes said first laser beam detector;
a first radio transmitter coupled to said first laser beam detector
and operable for broadcasting a first reference signal each time
said first laser beam strikes said first laser beam detector;
a second laser beam detector mounted to said first laser beam
transmitter and operable for detecting when said second laser beam
strikes said second laser beam detector;
a second radio transmitter coupled to said second laser beam
detector and operable for broadcasting a second reference signal
each time said second laser beam strikes said second laser beam
detector;
a laser beam receiver that is placed at a location at which the
position is to be determined and operable for detecting said first
and second laser beams during each rotation thereof, wherein said
laser beam receiver includes means for measuring the height at
which said laser beam receiver receives said first laser beam;
a radio receiver operable for receiving said first and second
reference signals; and
processing means coupled to said laser beam and radio receivers and
responsive to the timing of the detection of said laser beams by
said laser beam receiver relative to the receipt of said reference
signals by said radio receiver for determining the position in the
plane of the laser beams of said laser beam receiver relative to
the known locations of said laser beam transmitters and for
determining the elevation at each location according to said height
measured by said laser beam receiver, wherein said processing means
further includes means for recording the measured position and
elevation of each location.
24. An apparatus as recited in claim 23 wherein said processing
means includes means for determining the position of said laser
beam receiver at the intersection of first and second lines
projected in the datum plane and extending between respective first
and second laser beam transmitters and the laser beam receiver,
wherein the first and second lines as projected in the datum plane
form respective first and second angles in the datum plane with
respect to a reference line extending between said laser beams
transmitters and projected in the datum plane, wherein said means
includes means for determining said first angle according to the
ratio of the time interval between the detection of said first
laser beam by said laser beam receiver and the receipt of said
first reference signal by said radio receiver of the time interval
defined by the period of rotation of said first laser beam, and
wherein said means includes means for determining said second angle
according to the ratio of the time interval between the detection
of said second laser beam by said laser beam receiver and the
receipt of said second reference signal by said radio receiver to
the time interval defined by the period of rotation of said second
laser beam.
25. An apparatus comprising:
first and second reference stations positioned apart at known
locations during position sensing operations utilizing said
apparatus, wherein each reference station includes a laser beam
transmitter that projects a laser beam that periodically sweeps at
a constant angular velocity in a plane across an area in which
position sensing is to occur and that periodically strikes the
other reference station and a portable receiver, includes a
detector for detecting the laser beam from the other laser beam
transmitter, and includes a radio transmitter coupled to said
detector for broadcasting a reference signal upon each detection of
the other laser beam by said detector, and wherein one of said
laser beams is a datum laser beam that defines a datum plane;
a portable receiver that is placed at a location at which the
position is to be determined, wherein said portable receiver
includes a laser beam receiver operable for detecting the two laser
beams, includes a radio receiver operable for receiving the two
reference signals, and includes means for measuring the height at
which said datum laser beam strikes said laser beam receiver;
and
processing means coupled to said portable receiver and responsive
to the timing of the detection of said laser beams by said laser
beam receiver relative to the receipt of said reference signals by
said radio receiver for determining the position in said datum
plane of said portable receiver relative to the locations of said
laser beam transmitters, and responsive to the height measured by
said laser beam receiver for determining the elevation of each
location relative to said datum plane.
26. An apparatus as recited in claim 25 wherein said processing
means further includes means for recording the measured position
and elevation of said portable receiver relative to said laser beam
transmitters and includes means for transforming the measured
position and elevation of said portable receiver into one or more
alternative coordinate systems.
27. An apparatus as recited in claim 25 further comprising data
base means coupled to said processing means for defining the
positions relative to said reference stations of one or more
locations to be marked, and position error means coupled to said
processing means for indicating a positional error of said portable
receiver relative to a particular location to be marked, wherein
the position of said portable receiver defines the location to be
marked when the positional error is substantially equal to
zero.
28. An apparatus as recited in claim 25, wherein said processing
means further includes means for measuring the actual elevation of
a grading implement mounted on an earth-moving vehicle, wherein
said portable receiver is coupled to the grading implement for
movement therewith, wherein said apparatus further comprises data
base means for defining a desired elevation of the grading
implement as a function of the position of the grading implement,
and computational means for determining an elevation error of the
grading implement according to the difference between the measured
and desired elevations thereof.
29. An apparatus as recited in claim 28, further comprising
automatic control means responsive to said elevation error for
automatically adjusting the elevation of the grading implement to
reduce said elevation error.
30. An apparatus as recited in claim 28 further comprising means
for sensing the lateral position of the grading implement and for
determining a lateral positioning error of the grading implement
relative to a desired lateral position.
31. An apparatus as recited in claim 30, further comprising
automatic control means responsive to said elevation error for
automatically adjusting the elevation of the grading implement to
reduce said elevation error, and means for controlling the lateral
position of the grading implement by laterally shifting the grading
implement relative to the earth-moving vehicle to reduce said
lateral positioning error.
32. An apparatus as recited in claim 31 wherein said means for
controlling the lateral position of the grading implement further
includes means for automatically steering the earth-moving vehicle
to reduce said lateral positioning error.
33. A surveying apparatus for determining the position of one or
more locations to be surveyed, said apparatus comprising:
a first energy beam transmitter operable for projecting a first
energy beam that sweeps in a plane across the area to be
surveyed;
first reference signal means for generating a first reference
signal when said first energy beam is aligned with a first
reference line;
a second energy beam transmitter operable for projecting a second
energy beam that sweeps in a plane across the area to be surveyed,
wherein said first and second energy beam transmitters are
positioned apart during a surveying operation;
second reference signal means for generating a second reference
signal when said second energy beam is aligned with a second
reference line;
an energy beam receiver operable for detecting said first and
second energy beams, wherein said energy beam receiver is
sequentially positioned at each location to be surveyed;
a reference signal receiver operable for receiving said first and
second reference signals; and
processing means coupled to said energy beam and reference signal
receivers and responsive to the timing of the detection of said
energy beams relative to the receipt of said reference signals for
determining the position of said energy beam receiver at each
location to be surveyed relative to said reference lines and said
energy beam transmitters, wherein said processing means further
includes means for recording the measured position of each location
to be surveyed.
34. An apparatus as recited in claim 33 wherein one of said energy
beams is a datum beam that defines a datum plane, wherein said
surveying apparatus further comprises elevation measuring means for
determining the elevation of a location according to the height at
which said energy beam receiver detects said datum energy beam, and
wherein said processing means further includes means for recording
the measured elevation of said energy beam receiver.
35. An apparatus as recited in claim 34 wherein said processing
means further includes means for transforming the measured position
and elevation of said energy beam receiver into one or more
alternative coordinate systems.
36. An apparatus for positioning markers at one or more locations
to be marked, said apparatus comprising:
a first energy beam transmitter operable for projecting a first
energy beam that sweeps in a plane across the area to be
marked;
first reference signal means for generating a first reference
signal when said first energy beam is aligned with a first
reference line;
a second energy beam transmitter operable for projecting a second
energy beam that sweeps in a plane across the area to be marked,
wherein said first and second energy beam transmitters are
positioned apart during a marking operation;
second reference signal means for generating a second reference
signal when said second energy beam is aligned with a second
reference line;
an energy beam receiver operable for detecting said first and
second energy beams, wherein said energy beam receiver is
sequentially positioned at each location to be marked;
a reference signal receiver operable for receiving said first and
second reference signals;
processing means coupled to said energy beam and reference signal
receivers and responsive to the timing of the detection of said
energy beams relative to the receipt of said reference signals for
determining the position of said energy beam receiver relative to
said energy beam transmitters;
data base means coupled to said processing means for defining the
positions relative to said energy beam transmitters of the
locations to be marked; and
position error means coupled to said processing means for
indicating a positional error of said energy beam receiver relative
to a location to be marked, wherein the position of said energy
beam receiver defines the location to be marked when said
positional error is substantially equal to zero.
37. An apparatus as recited in claim 36 wherein one of said energy
beams is a datum energy beam that rotates in a datum plane, wherein
said apparatus further comprises elevation measuring means for
determining the elevation of each location to be marked according
to the height at which said energy beam receiver detects said datum
energy beam, wherein said data base means further defines a desired
elevation at each location to be marked, and wherein said position
error means includes means for determining an elevation error at
each location to be marked according to the difference between the
measured elevation and said desired elevation.
38. A reference station for use with another like reference station
and one or more portable receivers for position sensing, wherein
during a position sensing operation the reference stations are
spaced apart at known positions and the portable receiver is placed
at a location at which the position is to be determined, said
reference station comprising:
a housing;
an energy beam transmitter mounted to said housing and operable for
projecting a first energy beam that sweeps in a plane, wherein
during a position sensing operation said first energy beam
periodically strikes another reference station and a portable
receiver;
an energy beam detector mounted to said housing and operable for
detecting when the energy beam from the other reference station
strikes said energy beam detector during a position sensing
operation; and
reference signal means mounted to said housing and responsive to
the detection of the energy beam of the other reference station by
said energy beam detector for generating a reference signal to the
portable receiver.
39. A reference station as recited in claim 38 wherein said energy
beam transmitter includes means for sweeping said first energy beam
at a constant angular velocity in a plane across an area within
which position sensing is to occur.
40. A reference station as recited in claim 38 wherein said
reference signal means includes means for generating said reference
signal by broadcasting a radio frequency signal upon each detection
of the other energy beam.
41. A portable sensing station for use with two or more reference
stations for position sensing, wherein during a position sensing
operation the reference stations are spaced apart at known
positions, wherein each of the reference stations projects an
energy beam that sweeps in a plane and periodically strikes the
other reference station and said portable sensing station, and
wherein each of the reference stations generates a reference signal
when the energy beam from the other reference station strikes it,
said portable sensing station comprising:
an energy beam receiver operable for detecting energy beams
striking said energy beam receiver, wherein said energy beam
receiver is placed at a location at which the position is to be
determined;
a reference signal receiver operable for receiving each of the
reference signals from the reference stations; and
processing means coupled to said energy beam and reference signal
receivers and responsive to the timing of the detection of the
energy beams by said energy beam receiver relative to the receipt
of the reference signals by said reference signal receiver for
determining the position in the plane of the energy beams of said
energy beam receiver relative to the reference stations.
42. A portable sensing station as recited in claim 41 wherein one
of said energy beams is a datum energy beam that sweeps in a datum
plane, and wherein said portable sensing station further includes
elevation measuring means for determining the elevation of each
location to be surveyed according to the height at which said
energy beam receiver detects said datum energy beam, and includes
means for recording the measured position and elevation of said
portable sensing station.
43. A portable sensing station as recited in claim 42 wherein said
elevation measuring means includes a vertical support of adjustable
length for supporting said energy beam receiver and means for
measuring the extension of said vertical support at which said
energy beam receiver detects said datum energy beam.
44. A portable sensing station as recited in claim 42 wherein said
energy beam receiver includes a linearly extending array of energy
sensitive receiving cells including a datum cell, wherein said
linearly extending array crosses said datum plane, and wherein said
energy beam receiver is properly positioned for height measurement
when said datum cell detects said datum energy beam.
45. A portable sensing station as recited in claim 44 wherein said
energy beam receiver includes indicator means for indicating
whether receiving cells above or below said datum cell are
detecting said datum energy beam, wherein the detection of said
datum energy beam by a receiving cell positioned above said datum
cell indicates that said energy beam receiver is positioned too
low, and wherein the detection of said datum energy beam by a
receiving cell positioned below said datum cell indicates that said
energy beam receiver is positioned too high.
46. A portable sensing station as recited in claim 41, further
comprising data base means coupled to said processing means for
defining the positions relative to the reference stations of one or
more locations to be marked, and position error means coupled to
said processing means for indicating a positional error of said
energy beam receiver relative to a location to be marked, wherein
the position of said energy beam receiver defines the location to
be marked when said positional error is substantially equal to
zero.
47. A portable sensing station as recited in claim 46 wherein one
of said energy beams is a datum energy beam that rotates in a datum
plane, wherein said portable sensing station further includes
elevation measuring means for determining the elevation of each
location to be marked according to the height at which said energy
beam receiver detects said datum energy beam.
48. A portable sensing station as recited in claim 47 wherein said
data base means further defines a desired elevation at each
location to be marked, and wherein said position error means
includes means for determining an elevation error at each location
to be marked according to the difference between the measured
elevation and said desired elevation.
49. An apparatus for sensing the position and elevation of a
grading implement mounted on an earth-moving vehicle and for
determining an elevation error of the grading implement relative to
a desired elevation, wherein the desired elevation of the grading
implement at a particular position is the elevation that would
allow the earth-moving vehicle and attached grading implement to
produce a desired graded surface at that position, said apparatus
comprising:
a first energy beam transmitter operable for projecting a first
energy beam that sweeps in a plane across the area to be graded and
forms a datum plane;
first reference signal means for generating a first reference
signal when said first energy beam is aligned with a first
reference line;
a second energy beam transmitter operable for projecting a second
energy beam that sweeps in a plane across the area to be graded,
wherein said first and second energy beam transmitters are
positioned apart during operation of said apparatus;
second reference signal means for generating a second reference
signal when said second energy beam is aligned with a second
reference line;
an energy beam receiver operable for detecting said first and
second energy beams and for detecting the height at which said
first energy beam strikes said energy beam receiver, wherein said
energy beam receiver is coupled to a grading implement of an
earth-moving vehicle for movement therewith;
a reference signal receiver operable for receiving said first and
second reference signals; and
processing means coupled to said energy beam receiver and said
reference signal receiver and responsive to the timing of the
detection of said energy beams relative to the receipt of the
respective reference signals for determining the position of the
earth-moving vehicle relative to said energy beam transmitters, and
responsive to the height at which said first energy beam strikes
said energy beam receiver for determining the elevation of the
grading implement, wherein said processing means includes data base
means for defining the desired elevation of the grading implement
as a function of the position of the earth-moving vehicle, and
includes computational means for determining the elevation error of
the grading implement according to the difference between the
measured and desired elevations thereof.
50. An apparatus as recited in claim 49 further comprising
indicator means mounted on the earth-moving vehicle for displaying
the elevation error to the operator of the earth-moving
vehicle.
51. An apparatus as recited in claim 49 further comprising control
means coupled to the grading implement and responsive to the
elevation error for automatically adjusting the elevation of the
grading implement to reduce the elevation error.
52. An apparatus as recited in claim 49 wherein the desired graded
surface is inclined and the grading implement may necessarily be
sloped when producing the desired graded surface so that at any
given position of the grading implement the desired slope thereof
is a function of the orientation thereof, wherein said apparatus
further comprises means for determining the orientation and slope
of the grading implement, and wherein said processing means
includes means for determining the desired elevation and slope of
the grading implement as a function of the measured position and
orientation thereof.
53. An apparatus as recited in claim 52 further comprising control
means coupled to the grading implement for controlling the
elevation and slope of the grading implement to produce the desired
graded surface.
54. An apparatus as recited in claim 52 further comprising
indicator means mounted on the earth-moving vehicle and coupled to
said processing means for displaying to the operator of the
earth-moving vehicle the elevation error and a slope error, wherein
said slope error is the difference between the measured and desired
slope of the grading implement.
55. An apparatus as recited in claim 49 wherein said energy beam
receiver comprises a first energy beam receiver mast that is
coupled to one side of the grading implement for movement therewith
and a second energy beam receiver mast coupled to the opposite side
of the grading implement for movement therewith, and wherein said
processing means includes means for determining the slope of the
grading implement from the measured elevation of each side of the
grading implement.
56. A control system for an earth-moving vehicle for use in grading
a plot of land to a desired contour, wherein said earth-moving
vehicle includes a grading implement that defines the graded
surface, said control system comprising:
first and second reference stations spaced apart at known positions
and each including an energy beam transmitter operable for
projecting an energy beam that sweeps at a constant angular
velocity in a plane across the area to be graded and that
periodically strikes the other reference station and a receiver,
including an energy beam detector operable for detecting the energy
beam from the other reference station, and including a reference
signal transmitter responsive to the detection of the other energy
beam by said energy beam detector and operable for periodically
broadcasting a reference signal, wherein one of said energy beams
is denoted a datum energy beam that defines a datum plane for
elevation measurements;
a receiver mounted on an earth-moving vehicle, said receiver
including an energy beam receiver operable for detecting when and
the height at which said datum energy beam strikes said receiver,
wherein said energy beam receiver is coupled to a grading implement
for movement therewith, and including a reference signal receiver
operable for receiving said reference signals broadcast from said
reference stations;
position measuring means operatively coupled to said receiver and
coupled to the earth-moving vehicle for movement therewith and
responsive to the timing of the detection of the energy beams by
said energy beam receiver relative to the receipt of the respective
reference signals by said reference signal receiver for determining
the position of the grading implement relative to said reference
stations, and responsive to the height at which said datum energy
beam strikes said receiver for determining the elevation of the
grading implement relative to said datum plane;
data base means for defining the desired contour of the plot of
land in terms of desired elevations of the grading implement
relative to said datum plane as a function of the positions of the
grading implement relative to said reference stations;
processing means responsive to the measured position and elevation
of the grading implement and responsive to the desired elevation of
the grading implement for determining an elevation error of the
grading implement according to the difference between the measured
and desired elevations of the grading implement; and
automatic control means responsive to the elevation error for
automatically adjusting the elevation of the grading implement to
reduce the elevation error.
57. A control system as recited in claim 56 wherein the desired
graded surface is inclined and the grading implement is necessarily
sloped when producing the desired graded surface so that at any
given position of the grading implement the desired slope thereof
is a function of the orientation thereof, wherein said control
system further comprises means for determining the orientation and
slope of the grading implement, wherein said processing means
includes means for determining the desired slope of the grading
implement as a function of the measured position and orientation
thereof and for determining a slope error of the grading implement
according to the difference between the measured and desired slope
of the grading implement, and wherein said automatic control means
includes means responsive to said slope error for adjusting the
slope of the grading implement to reduce said slope error.
58. A control system as recited in claim 56 further comprising
means for sensing the lateral position of the grading implement and
for determining a lateral positioning error of the grading
implement relative to a desired lateral position, and means for
controlling the lateral position of the grading implement by
laterally shifting the grading implement relative to the
earth-moving vehicle to reduce said lateral positioning error.
59. A control system as recited in claim 58 wherein said means for
controlling the lateral position of the grading implement further
includes means for automatically steering the earth-moving vehicle
to reduce said lateral positioning error.
60. A method comprising the steps of:
projecting first and second energy beams from two transmitters that
are spaced apart, wherein each of said energy beams periodically
sweeps in a plane across an area within which position sensing is
to occur;
generating a first reference signal when said first energy beam is
aligned with a first reference line;
generating a second reference signal when said second energy beam
is aligned with a second reference line;
detecting said first and second energy beams with an energy beam
receiver that is placed at a location at which the position is to
determined;
receiving said first and second reference signals by a reference
signal receiver; and
determining the position of said energy beam receiver relative to
said reference lines and said transmitters according to the timing
of detection of said energy beams by said energy beam receiver
relative to the reception of said reference signals by said
reference signal receiver.
61. A method as recited in claim 60 further comprising the steps of
determining the positions of said transmitters relative to an
origin, and transforming the measured position of said energy beam
receiver relative to said reference lines and said transmitters
into a position relative to said origin.
62. A method as recited in claim 61 wherein the positions of first
and second bench marks are known relative to said origin, wherein
said reference lines extend between said two transmitters, and
wherein said step of determining the positions of said transmitters
relative to an origin includes the steps of positioning said energy
beam receiver at said first bench mark and detecting said first and
second energy beams and receiving said first and second reference
signals, determining the position of said first bench mark relative
to said transmitters according to the timing of detection of said
energy beams by said energy beam receiver while positioned at said
first bench mark relative to the reception of said reference
signals, repositioning said energy beam receiver at said second
bench mark and detecting said first and second energy beams and
receiving said first and second reference signals, determining the
position of said second bench mark relative to said transmitters
according to the timing of detection of said energy beams by said
energy beam receiver while positioned at said second bench mark
relative to the reception of said reference signals, and then
determining the positions of said transmitters relative to said
origin according to the measured positions of said bench marks
relative to said transmitters and according to the positions of
said bench marks relative to said origin.
63. A method as recited in claim 60 wherein said step of projecting
said first and second energy beams includes the steps of projecting
said first energy beam in a first plane and projecting said second
energy beam in a second plane that is substantially parallel to and
spaced apart from said first plane.
64. A method as recited in claim 63 wherein said step of projecting
said first and second energy beams includes the step of projecting
said first and second energy beams in substantially horizontal
planes.
65. A method as recited in claim 60 wherein said step of projecting
first and second energy beams includes the step of rotating said
first energy beam in a plane at a constant angular velocity and
rotating said second energy beam in a plane at a constant angular
velocity, and wherein said step of determining the position of said
energy beam receiver includes the steps of determining the
separation distance between said two transmitters, determining the
angle between said first reference line and a line extending from
said first energy beam transmitter to said energy beam receiver
according to the ratio of the time interval between the detection
of said first energy beam and the receipt of said first reference
signal to the time interval defined by the rotational period of
said first energy beam, determining the angle between said second
reference line and a line extending from said second energy beam
transmitter to said energy beam receiver according to the ratio of
the time interval between the detection of said second energy beam
and the receipt of said second reference signal to the time
interval defined by the rotational period of said second energy
beam, and determining the position of said energy beam receiver
according to said separation distance and said angular
positions.
66. A method as recited in claim 60 wherein said step of generating
a first reference signal includes the step of generating a first
reference signal when said first energy beam strikes a detector
mounted to the other transmitter, wherein said step of generating a
second reference signal includes the step of generating a second
reference signal when said second energy beam strikes a detector
mounted to the other transmitter, whereby said first and second
reference lines extend between said two transmitters.
67. A method as recited in claim 60 wherein said steps of
generating first and second reference signals includes the steps of
broadcasting respective first and second radio frequency signals,
and wherein said step of receiving said first and second reference
signals includes the step of receiving and distinguishing between
said first and second radio frequency signals.
68. A method as recited in claim 60 wherein said step of projecting
first and second energy beams includes the step of projecting one
of said energy beams as a datum energy beam in a datum plane, and
wherein said method further comprises the step of determining the
elevation of the location of the energy beam receiver according to
the height at which said energy beam receiver detects said datum
energy beam.
69. A method as recited in claim 68 wherein said step of
determining the elevation of the location of the energy beam
receiver includes the step of determining the elevation of said
datum plane and subtracting therefrom the height above ground at
which said energy beam receiver detects said datum energy beam.
70. A method as recited in claim 68 wherein said step of detecting
said first and second energy beams includes the step of adjusting
the elevation of an array of detector cells of said energy beam
receiver until a datum cell of said array detects said datum energy
beam, and wherein said step of determining the elevation of the
location of said energy beam receiver includes the step of
determining the height at which said datum cell detects said datum
energy beam.
71. A method for surveying as recited in claim 68 further
comprising the step of recording the measured position and
elevation of said energy beam receiver.
72. A method as recited in claim 60, further comprising the steps
of defining the positions relative to said energy beam transmitters
of one or more locations to be marked, positioning said energy beam
receiver near a location to be marked, indicating a positional
error of said energy beam receiver relative to the location to be
marked, repositioning said energy beam receiver until said
positional error is substantially equal to zero, and marking the
position of said energy beam receiver when said positional error is
substantially equal to zero.
73. A position sensing method comprising the steps of:
projecting a first laser beam in a first plane at a constant
angular velocity and projecting a second laser beam in a second
plane substantially parallel to said first plane at a constant
angular velocity, wherein said first and second laser beams are
transmitted from respective first and second laser beam
transmitters that are positioned apart by a known distance, wherein
the line between said laser beam transmitters defines a reference
line, and wherein said first and second laser beams periodically
sweep across an area with which position sensing is to occur and
also periodically strike the other laser beam transmitter;
broadcasting a first reference signal each time said first laser
beam strikes a detector mounted on said second laser beam
transmitter;
broadcasting a second reference signal each time said second laser
beam strikes a detector mounted on said first laser beam
transmitter;
detecting said first and second laser beams with a laser beam
receiver and receiving said first and second reference signals with
a reference signal receiver, wherein said receivers are placed at a
location at which the position is to be determined; and
determining the position of said laser beam receiver relative to
said laser beam transmitters in the plane of the laser beams as the
intersection of first and second lines extending in said plane from
respective first and second laser beam transmitters and forming
respective first and second angles with respect to said reference
line, wherein said first angle is determined according to the ratio
of the time interval between the detection of said first laser beam
and the receipt of said first reference signal to the time interval
defined by the period of rotation of said first laser beam, and
wherein said second angle is determined according to the ratio of
the time interval between the detection of said second laser beam
and the receipt of said second reference signal to the time
interval defined by the period of rotation of said second laser
beam.
74. A surveying method comprising the steps of:
projecting first and second energy beams from two transmitters that
are spaced apart, wherein each of said energy beams periodically
sweeps in a plane across the area to be surveyed, and wherein said
first laser beam defines a datum plane;
generating a first reference signal when said first energy beam is
aligned with a first reference line;
generating a second reference signal when said second energy beam
is aligned with a second reference line;
detecting said first and second energy beams with an energy beam
receiver that is positioned at a location to be surveyed;
determining the elevation of the location to be surveyed according
to the height at which said energy beam receiver detects said first
laser beam;
receiving said first and second reference signals by a reference
signal receiver; and
determining the position of said energy beam receiver at the
location to be surveyed relative to said reference lines and said
transmitters according to the timing of detection of said energy
beams by said energy beam receiver relative to the reception of
said reference signals by said reference signal receiver, and
recording the position and elevation of the location surveyed
according to the measured position and elevation of said energy
beam receiver.
75. A method for positioning markers at one or more locations to be
marked, said method comprising the steps of:
projecting first and second energy beams from two respective
transmitters that are spaced apart at known positions, wherein each
of said energy beams periodically sweeps in a plane across the area
to be marked;
defining the positions relative to said transmitters of the
locations to be marked;
generating a first reference signal when said first energy beam is
aligned with a first reference line;
generating a second reference signal when said second energy beam
is aligned with a second reference line;
positioning an energy beam receiver near a location to be
marked;
detecting said first and second energy beams with said energy beam
receiver and receiving said first and second reference signals with
a reference signal receiver;
determining the position of said energy beam receiver relative to
said transmitters according to the timing of detection of said
energy beams by said energy beam receiver relative to the reception
of said reference signals by said reference signal receiver;
indicating a positional error of said energy beam receiver relative
to the location to be marked;
repositioning said energy beam receiver until said positional error
is substantially equal to zero; and
marking the position of said energy beam receiver when said
positional error is substantially equal to zero.
76. A method as recited in claim 75, wherein one of said energy
beams is a datum beam that is projected in a datum plane, and
wherein said method further comprises the steps of selecting a
plurality of elevation-defining line segments along which the
desired contour of the land has a constant slope, wherein each line
segment has end points at which the position and desired elevation
is known; measuring the elevation of the location to be marked
according to the height at which said energy beam receiver detects
said datum energy beam when said positional error is substantially
equal to zero; determining the desired elevation of the location to
be marked; and determining the elevation error of the grading
implement according to the difference between the desired and
measured elevations at the location to be marked.
77. A method as recited in claim 76 wherein said step of
determining the desired elevation of the location to be marked
includes the steps of finding two elevation-defining line segments
near to and surrounding the location to be marked, finding the
elevations of two points on the line segments, wherein said two
points define a line through the location to be marked and wherein
the elevation of a point located on a line segment is found by
interpolating between the elevations of the two end points of that
line segment, and interpolating between the elevations of said two
points to determine the desired elevation of the location to be
marked.
78. A method for sensing the position and elevation of a grading
implement of an earth-moving vehicle and for determining an
elevation error of the grading implement relative to a desired
elevation, wherein the desired elevation of the grading implement
at a particular position is the elevation that would allow the
grading implement to produce a desired graded surface at that
position, and wherein the elevation error is the difference between
the actual and desired elevations of the grading implement, said
method comprising the steps of:
defining the desired elevations of the grading implement as a
function of the position of the grading implement throughout an
area to be graded;
projecting a first energy beam that sweeps in a datum plane across
the area to be graded;
generating a first reference signal when said first energy beam is
aligned with a first reference line;
projecting a second energy beam that sweeps in a plane across the
area to be graded, wherein said first and second energy beams are
transmitted from transmitters that are positioned apart;
generating a second reference signal when said second energy beam
is aligned with a second reference line;
detecting said first and second energy beams by an energy beam
receiver that is coupled to a grading implement of an earth-moving
vehicle for movement therewith;
receiving said first and second reference signals by a reference
signal receiver that is coupled to the earth-moving vehicle for
movement therewith;
determining the position of the grading implement relative to said
transmitters according to the timing of the detection of said
energy beams relative to the reception of said reference
signals;
measuring the elevation of the grading implement according to the
height at which said first energy beam strikes said energy beam
receiver; and
determining the elevation error of the grading implement according
to the difference between the measured elevation and the desired
elevation thereof.
79. A method as recited in claim 78, further comprising the step of
automatically controlling the elevation of the grading implement to
reduce said elevation error.
80. A method as recited in claim 78 further comprising the step of
displaying to the operator of the earth-moving vehicle the
elevation error.
81. A method as recited in claim 78, wherein the desired graded
surface is inclined and the grading implement is sloped when
producing the desired graded surface so that at any given position
of the grading implement the desired slope thereof is a function of
the orientation thereof, wherein the slope error is defined as the
difference between the actual and desired slope of the grading
implement, wherein said method further comprises the steps of
determining the orientation and slope of the grading implement,
determining the desired elevation and slope of the grading
implement as a function of the measured position and orientation
thereof, and determining the slope error of the grading implement
from the difference between the measured slope and the desired
slope thereof.
82. A method as recited in claim 81, further comprising the step of
automatically controlling the elevation and slope of the grading
implement to reduce said elevation and slope errors.
83. A method as recited in claim 81 further comprising the step of
displaying to the operator of the earth-moving vehicle said
elevation error and said slope error.
84. A method as recited in claim 78, wherein the desired graded
surface is inclined and the grading implement is sloped when
producing the desired graded surface, wherein said method further
comprises the steps of determining the position and elevation of
each side of the grading implement, determining the desired
elevation for each side of the grading implement as a function of
the measured position thereof, and determining the elevation error
of each side of the grading implement according to the difference
between the measured elevation and the desired elevation
thereof.
85. A method as recited in claim 84 wherein said energy beam
receiver comprises a first energy beam receiver that is coupled to
one side of the grading implement for movement therewith and a
second energy beam receiver coupled to the opposite side of the
grading implement for movement therewith, and wherein said step of
determining the position and elevation of each side of the grading
implement includes the steps of detecting said first and second
energy beams by each energy beam receiver, determining the position
of each side of the grading implement according to the timing of
the detection of said energy beams by each energy beam receiver
relative to the reception of said reference signals, and measuring
the elevation of each side of the grading implement according to
the height at which one of said energy beams strikes each energy
beam receiver.
86. A method as recited in claim 78 further comprising the step of
sensing the lateral position of the grading implement and for
determining a lateral positioning error of the grading implement
relative to a desired lateral position.
87. A method as recited in claim 86 further comprising the step of
automatically adjusting the lateral position of the grading
implement relative to the earth-moving vehicle to reduce said
lateral positioning error.
88. A method as recited in claim 86 further comprising the step of
automatically steering the earth-moving vehicle to reduce said
lateral positioning error.
89. A method for sensing the position and elevation of a grading
implement of an earth-moving vehicle and for determining an
elevation error of the grading implement relative to a desired
elevation, wherein the desired elevation of the grading implement
at a particular position is the elevation that would allow the
grading implement to produce a desired graded surface at that
position, and wherein the elevation error is the difference between
the actual and desired elevations of the grading implement, said
method comprising the steps of:
selecting a plurality of elevation-defining line segments along
which the desired contour of the land has a constant slope, wherein
each line segment has end points at which the position and desired
elevation is known;
projecting a first energy beam that sweeps in a datum plane across
the area to be graded, wherein all elevations are defined relative
to said datum plane;
generating a first reference signal when said first energy beam is
aligned with a first reference line;
projecting a second energy beam that sweeps in a plane across the
area to be graded, wherein said first and second energy beams are
transmitted from transmitters that are positioned apart at known
positions relative to said elevation-defining line segments;
generating a second reference signal when said second energy beam
is aligned with a second reference line;
detecting said first and second energy beams by an energy beam
receiver that is coupled to a grading implement of an earth-moving
vehicle for movement therewith;
receiving said first and second reference signals by a reference
signal receiver that is coupled to the earth-moving vehicle for
movement therewith;
determining the position of the grading implement relative to said
transmitters according to the timing of the detection of said
energy beams relative to the reception of said reference
signals;
measuring the elevation of the grading implement according to the
height at which said first energy beam strikes said energy beam
receiver;
determining the desired elevation of the grading implement
according to the steps of finding two elevation-defining line
segments near to and surrounding the position of the grading
implement, finding the elevations of two points on the line
segments, wherein said two points define a line through the
position of the grading implement and wherein the elevation of a
point located on a line segment is found by interpolating between
the elevations of the two end points of that line segment, and
interpolating between the elevations of said two points to
determine the desired elevation of the position of the grading
implement; and
determining an elevation error of the grading implement according
to the difference between the measured elevation and the desired
elevation thereof.
90. A method as recited in claim 89, further comprising the sep of
automatically controlling the elevation of the grading implement to
reduce said elevation error.
91. A method as recited in claim 89 further comprising the step of
displaying said elevation error to the operator of the earth-moving
vehicle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to surveying apparatus and
earth-grading machinery, and relates more particularly to
three-dimensional position sensing apparatus and methods that
utilize laser reference stations and one or more portable position
sensors.
2. Description of the Relevant Art
According to conventional practice, the process of transforming a
tract of land into a graded surface involves several tasks,
typically beginning with the task of surveying the land in order to
create a contour map or other graphical representation of the
pre-existing state of the land. Surveying involves the delineation
of the form, extent, and position of the tract of land based on
linear and angular measurements of the land. According to
conventional practice, surveying is at least a two person job, with
one person operating a measuring instrument from a generally
stationary position and the other person transporting and
positioning a grade rod or other reference to be sighted by the
measuring instrument. The measuring instrument, such as a transit,
theodolite, distance meter, or total station, is positioned at a
known distance and angle from a reference, or bench mark, position.
The grade rod is sequentially positioned at one or more locations,
and at each such location, the distance and angle of the grade rod
with respect to the position of the measuring instrument is
determined and recorded. Distances may be measured manually with a
steel tape or chain, or may be measured optically by the measuring
instrument utilizing various means such as a retroreflector on the
grade rod. Angles are typically measured in both horizontal and
vertical planes, with an azimuth angle defined as the horizontal
angle measured clockwise from north, and a zenith angle defined as
the vertical angle measured downward from the vertical.
From the distance and angle information obtained in the survey, and
through application of the principles of geometry and trigonometry,
the surface of the tract of land can be characterized and presented
in graphical form. The position or location of any point on the
tract of land can be represented in a variety of three-dimensional
coordinate systems such as X,Y,Z, or R,.THETA.,Z, where X,Y,Z
denotes a Cartesian coordinate system in which the X-Y plane is
horizontal and the Z axis is vertical, and where R,.THETA.,Z
denotes a cylindrical coordinate system in which the R-.THETA.
plane is horizontal and the Z axis is vertical. The X,Y or
R,.THETA. coordinates are measured in a horizontal plane with
respect to some bench mark position, while the Z coordinate is the
elevation measured with respect to some horizontal reference plane,
such as mean sea level.
After the tract of land has been surveyed, a site plan can be drawn
up to define what the contours and elevations of the land should be
after grading. In accordance with conventional practices, the site
is then marked with stakes in order to guide the operators of
earth-moving equipment while they grade the land into conformity
with the site plan. The process of marking involves first defining
on the site plan the coordinates of various key locations to be
marked, and then placing stakes on the land at those locations. The
task of marking the land can utilize the same surveying apparatus
described above. The grade rod is roughly positioned near a
location to be marked, and its position is determined by the
measuring instrument. If the grade rod is not exactly positioned at
the location to be marked, the position is noted and the grade rod
is repositioned and remeasured until the measuring instrument
verifies that the grade rod is positioned at the location to be
marked. A stake or other marker is then driven into the ground at
that point. Like surveying, the process of marking a tract of land
is also a task that requires at least two trained people.
In order to designate the desired elevation at the marked
locations, the stakes are typically marked with indications of the
depth of fill or cut needed to create the desired graded surface at
those locations. Such fill or cut information can be determined
according to the elevational differences between the contour map of
the existing site and the site plan.
After the tract of land has been marked, earth-moving equipment can
be used for grading the site. The operators of the earth-moving
equipment are guided by the marker stakes in determining where to
cut and where to fill. Care must be exercised to avoid damaging the
stakes during the grading operation. The site may need to be
re-surveyed during or after completion of the grading to verify the
accuracy of the graded surface. With the necessary tasks of
surveying, marking, and resurveying, the convention practice of
transforming a tract of land into a graded surface is unavoidably
labor intensive, even apart from the actual grading operations.
SUMMARY OF THE INVENTION
In accordance with the illustrated preferred embodiment, the
present invention provides a three-dimensional position sensing
system utilizing two or more stationary laser reference stations
and one or more portable position sensors. The position of the
portable position sensor is determined by means associated with the
portable position sensor by measuring the angular position of the
portable position sensor with respect to each laser reference
station. The position sensing system of the present invention
encompasses a reference station apparatus, a portable sensing
station apparatus, a surveying apparatus and method, a marking
apparatus and method, a grading implement sensing apparatus and
method, and a grading implement control apparatus and method, all
of which have certain apparatus and method steps in common, and all
of which are useful in transforming a tract of land into a graded
surface.
One aspect of the present invention is a position sensing system
comprising both apparatus and method for determining the position
of one or more locations. The apparatus includes: a first energy
beam transmitter that is operable for projecting a first energy
beam that sweeps across an area in which position sensing is to
occur, first reference signal means for generating a first
reference signal when the first energy beam is aligned with a first
reference line, a second energy beam transmitter that is operable
for projecting a second energy beam that sweeps across the area,
wherein the first and second energy beam transmitters are
positioned apart during a position sensing operation, second
reference signal means for generating a second reference signal
when the second energy beam is aligned with a second reference
line, an energy beam receiver that is operable for detecting the
first and second energy beams and that is sequentially positioned
at each location at which the position is to be sensed, a reference
signal receiver that is operable for receiving the first and second
reference signals, and processing means coupled to the energy beam
and reference signal receivers and responsive to the timing of the
detection of the energy beams relative to the receipt of the
reference signals for determining the position of the energy beam
receiver relative to the reference lines and the energy beam
transmitters in the plane of the energy beams.
The position sensing method includes the steps of: projecting first
and second energy beams from the two energy beam transmitters,
wherein each of the energy beams periodically sweeps across the
area in which position sensing is to occur, generating a first
reference signal when the first energy beam is aligned with a first
reference line, generating a second reference signal when the
second energy beam is aligned with a second reference line,
detecting the first and second energy beams with the energy beam
receiver when positioned at a location to be sensed, receiving the
first and second reference signals by the reference signal
receiver, and determining the position of the energy beam receiver
relative to the reference lines and the transmitters in the plane
of the energy beams according to the timing of detection of the
energy beams by the energy beam receiver relative to the reception
of the reference signals by the reference signal receiver.
In the position sensing system, each reference signal means is
preferably mounted on the opposite energy beam transmitter, so that
the reference lines coincide and extend between the transmitters.
Likewise, the energy beam receiver, reference signal receiver, and
processing means are preferably packaged together into a portable,
position-sensing station. Also preferably, the position of the
energy beam receiver in the plane of rotation of the energy beams
is determined by a triangulation technique, by finding the angular
position of the energy beam receiver relative to the reference line
with the two transmitters located at the vertices of the two
angles. Each angle is determined according to the ratio of two time
intervals, where the first time interval is measured between the
detection of an energy beam by the energy beam receiver and the
receipt of the corresponding reference signal by the reference
signal receiver and the second time interval is equal to the
rotational period of the energy beam, which is measured between the
receipt of two succeeding reference signals. In other words, if the
first time interval is equal to one-eighth of the period of
revolution of the energy beam, then the angle is 360.degree./8, or
45.degree.. The positions of the reference stations and the
separation distance therebetween in the plane of the energy beams
can be determined through a calibration procedure by position
sensing the locations of two bench mark locations.
The energy beams preferably are laser beams projected at constant
angular velocities in parallel planes. The reference signal means
is a radio transmitter that broadcasts the reference signal once
during each revolution of the opposite laser beam. Also preferably,
the portable sensing station includes elevation measuring means for
determining the ground elevation of the location of the energy beam
receiver according to the height at which the energy beam receiver
detects one of the energy beams, which is denoted as a datum energy
beam. In the special case where the energy beam is projected in a
horizontal datum plane, the elevation of the location is equal to
the elevation of the datum energy beam minus the height at which
the datum energy beam strikes the energy beam receiver. If the
datum energy beam is tilted so that the datum plane is not
horizontal, a correction to the measured elevation can be made
based on the measured position of the energy beam receiver in the
datum planes.
Another aspect of the position sensing system of the present
invention is the reference station itself, which is designed for
use with another like reference station and a portable sensing
station for surveying, marking, or other position sensing
operations. During operation, two or more reference stations are
spaced apart at known positions and the portable sensing station is
sequentially positioned at one or more locations at which the
positions are to be sensed. The reference station includes an
energy beam transmitter, an energy beam detector, and reference
signal means, preferably all mounted in a housing that supports the
reference station in an upright orientation. The energy beam
transmitter is operable for projecting an energy beam that sweeps
in a plane and periodically strikes both the other reference
station and the portable sensing station. The energy beam detector
is operable for detecting the energy beam from the other reference
station and triggering the reference signal means, which, in
response, generates a reference signal for use by the portable
sensing station. Preferably, the energy beams are laser beams, each
of which is projected at a constant angular velocity in a
horizontal plane. Also preferably, the reference signal means is a
radio transmitter broadcasting the reference signal once during
each revolution of the opposite laser beam.
Another aspect of the present invention is a portable sensing
station, which is used with two or more stationary reference
stations for surveying, marking, or other position sensing
operations. The portable sensing station includes an energy beam
receiver, a reference signal receiver, and processing means, of
which at least the energy beam receiver is positioned at the
location at which the position is to be sensed. The energy beam
receiver is operable for detecting the energy beams projected by
the reference stations, while the reference signal receiver is
operable for receiving the reference signals generated by the
reference stations. The processing means is functionally coupled to
the energy beam and reference signal receivers and is responsive to
the timing of the detection of the energy beams by the energy beam
receiver relative to the receipt of the respective reference
signals by the reference signal receiver for determining the
position of the energy beam receiver relative to the reference
stations in the plane of rotation of the energy beams. Preferably,
the processing means includes a programmed portable computer that
is transported with the energy beam and reference signal receivers.
Also preferably, the portable sensing station includes elevation
measuring means for determining ground elevation according to the
height at which the energy beam receiver detects one of the energy
beams.
Another aspect of the position sensing system of the present
invention is an apparatus and method for surveying one or more
locations. The surveying apparatus is similar to the position
sensing apparatus summarized above, but further includes means for
recording the planar positions relative to the energy beam
transmitters and elevations relative to a datum energy beam of the
locations to be surveyed. The method for surveying is similar to
the position sensing method summarized above, but further includes
the step of recording the positions and elevations of the locations
surveyed.
A further aspect of the position sensing system of the present
invention is an apparatus and method for positioning markers at one
or more locations to be marked. The marking apparatus is similar to
the position sensing apparatus summarized above, but further
includes data base means coupled to the processing means for
defining the planar positions relative to the energy beam
transmitters of the locations to be marked, and position error
means coupled to the processing means for indicating a positional
error of the energy beam receiver relative to a location to be
marked, wherein the position of the energy beam receiver defines
the location to be marked when the positional error is
substantially equal to zero.
The method for positioning markers includes the capability of
finding at each location to be marked the difference in elevation
between a desired elevation and a measured elevation thereof, where
the desired elevations are calculated by interpolating between two
nearby, elevation-defining line segments. The method is similar to
the position sensing method summarized above, but further includes
the steps of: selecting a plurality of elevation-defining line
segments along each of which the contour of the land is assumed
straight, i.e., having a constant slope, where each line segment
extends between two end points at each of which the planar position
and desired elevation is known; defining the planar positions
relative to the transmitters of the locations to be marked;
positioning the energy beam receiver near a location to be marked;
indicating a positional error of the energy beam receiver relative
to the location to be marked; repositioning the energy beam
receiver until the positional error is substantially equal to zero;
marking the position of the energy beam receiver when the
positional error is substantially equal to zero; measuring the
elevation of the location to be marked according to the height at
which the energy beam receiver detects the datum energy beam when
the positional error is substantially equal to zero; determining
the desired elevation of the location to be marked according to the
steps of finding two elevation-defining line segments that are
closest in position to and surround the location to be marked,
finding the elevations of two points on the line segments, wherein
the two points define a line extending through the location to be
marked and wherein the elevation of a point located on a line
segment is found by interpolating between the elevations of the two
end points of that line segment, and interpolating between the
elevations of said two points to determine the desired elevation of
the location to be marked; and determining the difference between
the desired and measured elevations at the location to be marked as
an elevation error.
Preferably, the data base means of the marking apparatus is
incorporated with the processing means into a programmed portable
computer that is transported with the energy beam and reference
signal receivers. The programmed computer is preferably also used
to determine the positional error of the energy beam receiver
relative to the location to be marked. Also preferably, the
calculations involved in determining the desired elevations and
elevation errors of the locations to be marked are accomplished by
the computer.
A still further aspect of the position sensing system of the
present invention is an apparatus and method for sensing the
position and elevation of a grading implement mounted on an
earth-moving vehicle and for determining an elevation error of the
grading implement relative to a desired elevation, wherein the
desired elevation of the grading implement at a particular position
is the elevation that would allow the earth-moving vehicle and
attached grading implement to produce a desired graded surface at
that position. In addition to the position sensing apparatus
summarized above, the implement sensing apparatus includes data
base means for defining the desired elevation of the grading
implement as a function of the position of the earth-moving vehicle
and grading implement, and includes computational means for
determining the elevation error of the grading implement according
to the difference between the measured and desired elevations
thereof. The energy beam receiver is coupled to the grading
implement, while the reference signal receiver is coupled to either
the grading implement or the earth-moving vehicle. In addition to
determining the position f the earth-moving vehicle relative to the
energy beam transmitters, the processing means is also responsive
to the height at which one of the energy beams strikes the energy
beam receiver for determining the elevation of the grading
implement and for determining the elevation error of the grading
implement. The implement sensing apparatus may additionally include
means for sensing the lateral position of the grading implement and
for determining a lateral positioning error of the grading
implement relative to a desired lateral position.
In addition to the steps comprising the position sensing method
summarized above, the method for implement sensing further includes
the steps of defining the desired elevations of the grading
implement as a function of position of the grading implement
throughout an area to be graded, determining the position of the
grading implement relative to the transmitters according to the
timing of the detection of the energy beams relative to the
reception of the reference signals, where the energy beam receiver
is coupled to the grading implement and the reference signal
receiver is coupled to the earth-moving vehicle, measuring the
elevation of the grading implement according to the height at which
one of the energy beams strikes the energy beam receiver, and
determining the elevation error of the grading implement from the
difference between the measured elevation and the desired elevation
thereof.
Still another aspect of the position sensing system of the present
invention is a control system and method for controlling the
grading implement of an earth-moving vehicle during the grading of
a plot of land to a desired contour. The control system includes:
first and second reference stations as summarized above and spaced
apart at known positions, a receiver including an energy beam
receiver coupled to the grading implement and a reference signal
receiver mounted on the earth-moving vehicle, position measuring
means operatively coupled to the receiver and operable for
determining the position of the grading implement relative to the
reference stations and for determining the elevation of the grading
implement relative to a datum plane, data base means for defining
the desired contour of the plot of land in terms of desired
elevations of the grading implement relative to the datum plane as
a function of the positions of the grading implement relative to
the reference stations, processing means responsive to the measured
position and elevation of the grading implement and responsive to
the desired elevation of the grading implement for determining an
elevation error of the grading implement according to the
difference between the measured and desired elevations of the
grading implement, and automatic control means responsive to the
elevation error for automatically adjusting the elevation of the
grading implement to reduce the elevation error. The implement
control apparatus may additionally include means for sensing the
lateral position of the grading implement, for determining a
lateral positioning error of the grading implement relative to a
desired lateral position, and means for controlling the lateral
position of the grading implement by laterally shifting the grading
implement relative to the earth-moving vehicle and/or by steering
the earth-moving vehicle.
The method for controlling the grading implement is similar to the
above-summarized method for implement sensing with the additional
step of automatically adjusting the elevation of the grading
implement to reduce the elevation error. This method may further
include the step of automatically adjusting the lateral position of
the grading implement to reduce the lateral positioning error.
The many features of the various aspects of the position sensing
system of the present invention provide many advantages over
conventional apparatus and methods of surveying, marking, and
implement sensing and control. One feature of the present invention
is its adaptability to several tasks, namely surveying, marking,
and implement sensing and control. Another feature is that the
comprehensive data base created during the surveying process can be
reused throughout the subsequent processes of marking and implement
sensing and control. Another feature is that the tasks of data
gathering and processing can be accomplished efficiently and
accurately by the programmed computer, instead of laboriously by a
skilled surveyor. Still another feature of the present invention is
that all three positional coordinates of a location can be
determined in one operation. A further feature of the present
invention is that the position-defining data is available at the
portable sensing station, so that the data can be utilized
immediately at the portable sensing station for operations such as
marking and implement sensing and control. A still further feature
is that multiple portable sensing stations can be utilized with the
two reference stations in order to reduce the time required to
accomplish a position sensing task. Another feature is that more
than two reference stations can be utilized for increased accuracy
and coverage. A further feature is that the location of the
transmitters need not be known beforehand and can be determined
through the use of the position sensing apparatus by a calibration
procedure using as few as two bench mark locations.
As a surveying or marking apparatus and method, the present
invention provides significant advantages over conventional
surveying apparatus and methods. By utilizing the surveying or
marking apparatus of the present invention, the process of
surveying or marking can be accomplished by a single operator
manning the portable sensing station, instead of two or more
operators, as required by conventional methods. Also, that single
operator need not be highly skilled, due to the fact that the
computer of the present invention handles all of the necessary data
processing. As noted above, several operators, each with their own
portable sensing station, can work simultaneously to significantly
reduce the time required to survey or mark a tract of land. Another
way to speed up the surveying or marking process utilizing the
present invention would be to mount the portable sensing station on
a vehicle that can be speedily driven from location to location.
Sites can be resurveyed during or after grading in order to verify
the accuracy of grading by conventional methods. Sites can also be
resurveyed after physical structures such as curbs or foundations
have been erected to allow the site plan to be adapted to the
as-constructed state of the site.
As a grading implement sensing or control apparatus and method, the
present invention provides significant advantages over conventional
apparatus and methods. Since the positions of the grading equipment
is continuously sensed, the conventional intermediate step of
marking the site with stakes can be eliminated. As with the
surveying or marking processes, the grading process can also be
accelerated using multiple portable sensing stations, each
independently sensing and/or controlling the grading implement of
an earth-moving vehicle. Any resurveying or checking of the graded
surface can be accomplished easily using the same reference
stations that have been set up for implement sensing and control.
By automatically supplying grade control data to the graders,
rather than grading to stakes or auxiliary grading references, time
is saved and errors are avoided. In contrast to prior art apparatus
for controlling implement elevation with respect to a laser datum
plane, in which the implement elevation is limited to a fixed,
predetermined distance below the laser datum plane, the present
invention allows the use of variable elevations and slopes of the
implement. In short, the present invention significantly
streamlines the task of transforming a tract of land into the
graded surface defined by the site plan.
The features and advantages described in the specification are not
all inclusive, and particularly, many additional features and
advantages will be apparent to one of ordinary skill in the art in
view of the drawings, specification and claims hereof. Accordingly,
resort to the claims is necessary to determine the scope of such
inventive subject matter.
Moreover, it should be noted that the language used in the
specification has been principally selected for readability and
instructional purposes, and may not have been selected to delineate
or circumscribe the inventive subject matter, which applies to a
broad range of position sensing tasks. While certain embodiments of
the present invention are shown as being used in conjunction with
an earth-moving vehicle, it should be understood that the present
invention may also be used on other grading implement or tool
carrying vehicles such as bulldozers, trenching machines,
curb-laying machines, and the like. The term "earth-moving vehicle"
is intended to cover all such alternative vehicles or apparatus in
conjunction with which it would be apparent to one skilled in the
art to use the present invention. Likewise, the term "grading
implement" is intended to cover all grading blades, tools, and
other apparatus in conjunction with which it would be apparent to
one skilled in the art to use the present invention. Likewise, the
term "grading" is intended to cover all grading, earth-moving,
ditch digging, pipe laying, curb constructing, and other like
processes in conjunction with which it would be apparent to one
skilled in the art to use the present invention. The terms
"position" and "planar position" are used herein as referring to a
location, position, or locality defined in terms of a planar
position with respect to a known, or bench mark, position, while
the term "elevation" is meant to refer to the elevation of the
location, position, or locality measured orthogonally with respect
to a reference plane. Typically, although not necessarily, the
reference plane is horizontal and the planar position is denoted in
terms of X,Y or R,.THETA. coordinates and the elevation is denoted
in terms of a Z coordinate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a position sensing apparatus
according to the present invention.
FIG. 2 is a top plan view of the position sensing apparatus of FIG.
1.
FIG. 3 is a side elevation view of the position sensing apparatus
of FIG. 1.
FIG. 4 is a block diagram of the position sensing apparatus of FIG.
1, illustrating two reference stations and a portable sensing
station.
FIG. 5 is a timing diagram of various signals processed by the
position sensing apparatus of FIG. 1.
FIG. 6 is a perspective view of a portable sensing station of the
position sensing apparatus of FIG. 1.
FIG. 7 is a perspective detail view of a laser beam sensor portion
of the portable sensing station of FIG. 6.
FIG. 8 is a block diagram of a datum indicator circuit of the
portable sensing station of FIG. 6.
FIG. 9 is a schematic diagram of a timer circuit of the portable
sensing station of FIG. 6.
FIG. 10 is a flow chart of a programmed computer portion of the
portable sensing station of FIG. 6.
FIG. 11 is a plan view diagram showing placement of the position
sensing apparatus of FIG. 1 relative to two Cartesian coordinate
systems.
FIG. 12 is a plan view diagram illustrating a calibration of the
position sensing apparatus of FIG. 1 to two bench mark
locations.
FIG. 13 is a block diagram of a processor utilized as part of the
portable sensing station of the present invention when used for
position marking.
FIG. 14 is a side elevation view of a receiver mast of the present
invention attached to an earthmoving vehicle for implement position
sensing or control.
FIG. 15 is a block diagram of a processor utilized as part of the
portable sensing station when used for implement position sensing
or control.
FIG. 16 is a perspective view, partially broken away, of a laser
receiver mast.
FIG. 17 is a top plan view of an earth-moving vehicle employing the
present invention to follow a desired lateral contour.
FIG. 18 is a perspective view of an earth-moving vehicle with two
laser receiver masts installed thereupon.
FIG. 19 is a plan view diagram illustrating the process of position
and orientation sensing of the earth-moving vehicle of FIG. 18.
FIG. 20 is a perspective view of an earth-moving vehicle with a
single receiver mast installed thereupon.
FIG. 21 is a perspective view of the position sensing apparatus of
FIG. 1 set up for surveying a tract of land.
FIG. 22 is a contour map of the tract of land of FIG. 21.
FIG. 23 is a site plan illustrating elevation-defining line
segments that define the desired graded surface of the tract of
land of FIG. 21.
FIG. 24 is a grid map illustrating the depth of cut or fill that
will be required to transform the tract of land of FIG. 21 into the
desired graded surface defined by the site plan of FIG. 23.
FIG. 25 is a perspective view of a portable sensing station mounted
on a surveying vehicle, according to an alternative embodiment of
the present invention.
FIG. 26 is a perspective view of a reference station mounted on a
vehicle, according to an alternative embodiment of the present
invention.
FIG. 27 is a plan view diagram of an alternative embodiment of the
present invention wherein three reference stations are
employed.
FIG. 28 is a plan view diagram of an alternative embodiment of the
present invention wherein a laser beam detector station is located
apart from the two reference stations.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 through 28 of the drawings depict various preferred
embodiments of the present invention for purposes of illustration
only. One skilled in the art will readily recognize from the
following discussion that alternative embodiments of the structures
and methods illustrated herein may be employed without departing
from the principles of the invention described herein.
The preferred embodiment of the present invention is a
three-dimensional position sensing apparatus and method utilizing
laser reference stations and one or more portable position sensors.
The position sensing apparatus and method of the present invention
will first be described in relation to the tasks of surveying and
marking, and will later be described in relation to the tasks of
grading implement sensing and controlling.
As shown in FIGS. 1, 2, 3, and 4, a position sensing apparatus 10
according to the present invention preferably includes two
reference stations 12 and a portable sensing station 13. The
portable sensing station 13 in turn comprises a receiver 14 and a
portable computer 16. The two reference stations 12 are positioned
apart at stationary locations adjacent to an area to be surveyed or
marked, while the portable sensing station 13 is sequentially
positioned at various locations throughout the area to be surveyed
or marked. The positions of the reference stations 12 are known
either by placing the reference stations at known locations
relative to some origin or reference coordinate system, or by
placing the reference stations at unknown locations and
subsequently determining the positions of the reference stations by
a calibration procedure, which will be described below in further
detail.
As will be apparent from the following description, the position
sensing apparatus 10 is operable for determining the planar
position of the receiver 14 with respect to the planar positions of
the two reference stations 12, and is also operable for determining
the elevation at the receiver with respect to the elevation of one
of the reference stations. The planar position of the receiver 14
is preferably determined in a datum plane, preferably but not
necessarily horizontal, while the elevation at the receiver is
preferably measured vertically.
Each of the reference stations 12 preferably includes a laser
transmitter 18, a laser detector 20, and a radio signal transmitter
22 that is coupled to the laser detector 20, as shown in FIG. 4.
Each laser transmitter 18 projects an energy beam that sweeps
across the area to be surveyed or marked. The laser transmitter 18
projects a laser beam that rotates in a plane at a constant angular
velocity. Once each revolution, the laser beam strikes both the
receiver 14 and the laser detector 20 mounted on the other
reference station 12.
Each reference station 12 includes a housing 26 that is supported
in an upright orientation by a tripod 28, shown in FIGS. 1 and 3.
Within the housing 26 is a laser source 30 that projects a laser
beam vertically upward to a rotating or oscillating lens 32, which
reflects the laser beam into a horizontal planar path. The
rotational or oscillatory period of the projected laser beam is
preferably about one tenth of a second, which is equivalent to a
frequency of about ten revolutions or oscillations per second. The
reference station 12 need not project the laser beam over a
complete circle; an arc that covers the area to be surveyed or
marked plus the other reference station is sufficient. The need to
limit off-site transmission of the laser beams may dictate the use
of shutters to restrict the projection of the laser beam in certain
directions. It is preferable that the laser beam be projected in a
horizontal plane, however, inclined planes may also be utilized
within the scope of the present invention. Since in some
applications, such as surveying and marking, it is preferable for
the laser beams to rotate in a horizontal plane, much of the
following description will refer to the laser plane as horizontal.
Such references are not to be taken as limitations, since the
position sensing apparatus and methods can operate with
non-horizontal laser planes.
Laser transmitters similar to the laser transmitters 18 are known
in the art, one example of which is disclosed in U.S. Pat. No.
3,588,249 issued to R. H. Studebaker, and other examples of which
are available as a commercial product from Spectra Physics of
Dayton, Ohio as laser models 945 and 1045.
Preferably, the two reference stations 12 are erected so that the
horizontal planes 34 and 36 formed by the two projected laser beams
are spaced apart by a separation distance 37, as shown in FIG. 3.
Each of the two laser detectors are mounted on their respective
reference stations 12 at the vertical position defined by the laser
plane 34 and 36 projected by the opposite reference station. In the
case of reference station 38, shown at the left of FIGS. 1-4, a
laser detector 40 is positioned above the laser plane 34 projected
from that reference station by a distance equal to the separation
distance 37. In the case of reference station 42, shown at the
right of FIGS. 1-4, a laser detector 44 is positioned below the
laser plane 36 projected from that reference station by a distance
equal to the separation distance 37. Each laser detector 20
triggers its associated radio signal transmitter 22 to broadcast a
radio signal each time the laser beam from the opposite reference
station 12 strikes the laser detector 20. An antenna 46 located at
the top of each reference station 12 is connected to the radio
transmitter 22 to facilitate the broadcast of the radio signal.
Preferably, the two radio signals are broadcast at different
frequencies or are otherwise encoded so that the receiver 14 can
distinguish between them. The line extending between the two
reference stations 12 defines a reference line 48 that will be used
to determine the relative positions of the receiver 14.
As shown in FIG. 4, the receiver 14 includes a laser receiver 50, a
radio signal receiver 52, and means 54 for measuring the elevation
(Z) of the location to be surveyed or marked. The laser receiver 50
is preferably a photocell or other sensor that is responsive to
impinging energy from the two incident laser beams, while the radio
signal receiver 52 is responsive to the radio signals broadcast by
the two radio signal transmitters 22. The laser receiver 50, the
radio signal receiver 52, and the elevation measuring means 54 are
electrically coupled through an interface circuit 56 to the
portable computer 16.
The computer 16 is programmed in such a way, as described below, to
enable it to calculate the position of the receiver 14 in the plane
of the laser beams with respect to the positions of the reference
stations 12 and the reference line 48 according to the relative
timing of reception of the laser and radio signals by the laser and
radio signal receivers 50 and 52. Given that each laser beam
rotates at a constant angular velocity, and that a radio signal is
broadcast each time the laser beam is aligned with the reference
line 48, the angle 58 or 60 (FIG. 2) between the reference line 48
and a line 62 or 64 between a reference station 40 or 42 and the
receiver 14 is proportional to the ratio of the time interval
between the reception of the radio signal and the reception of the
laser beam at the receiver to the time interval of the period of
rotation of the laser beam.
The radio receiver 52 of the receiver 14 periodically receives the
radio signal that is broadcast each time the laser beam from
reference station 38 hits the detector 44 on reference station 42,
which occurs each time the laser beam is aligned with the reference
line 48. Each such reception of the radio signal is denoted at
points 66 on the time line in FIG. 5. The laser receiver 50 of the
receiver 14 periodically detects the laser beam projected from
reference station 38, as denoted by points 68 on the time line. The
time interval 70 between successive points 66 is equal to the
period of rotation of the laser beam projected by reference station
38, while the time interval 72 between a point 66 and a subsequent
point 68 is the time required for the laser beam to swing around
from the reference line 48 to line 62. Thus, the ratio of time
interval 72 to time interval 70 multiplied by 2.pi. is equal to the
angle 58 in radians, or, the ratio multiplied by 360.degree. is
equal to the angle 58 in degrees. Likewise, the angle 60 between
reference line 48 and line 64 with reference station 42 at the
vertex thereof is determined from the ratio of time interval 74 to
time interval 76. Time interval 74 is equal to the time interval
between the reception by the radio signal receiver 52 of the radio
signal broadcast when the laser beam projected from reference
station 42 hits detector 40 and the reception by the laser receiver
50 of the laser beam from reference station 42, which occurs each
time the laser beam is aligned with the reference line 48. Time
interval 76 is equal to the period of rotation of the laser beam.
Note that the time intervals 70 and 76, which are equal to the
periods of rotation of the two laser beams, could alternatively be
determined between successive receptions of the laser beams by the
receiver 14 rather than successive receptions of the radio signals.
The foregoing assumes that both laser beams rotate in the clockwise
direction at constant angular velocity and that the two angles 58
and 60 are measured clockwise from the reference line 48. As
described below, the computer 16 does the necessary calculations to
compute the angles and records the results.
The portable sensing station 13 is also operable for determining
the elevation at the position of the receiver 14 with respect to
one of the laser planes. If laser plane 36 is denoted as a datum or
reference plane, as shown in FIG. 3, then the elevation, Z, of the
ground at the foot or base of the receiver 14 with respect to the
laser plane 36 can be determined from the height at which the laser
plane 36 intersects the laser receiver 50. One type of receiver
design is shown in FIG. 6 to include an extensible rod 80, an
extension measuring device 82, a laser receiver 50, a radio
receiver 52, and a receiving antenna 84. The extensible rod 80
serves to support the laser receiver 50 at the proper elevation for
intercepting the laser beams. The extension measuring device 82,
which can be as simple as a tape measure, provides means for
determining the height at which the datum laser beam intersects the
laser receiver according to the extension of the extensible rod 80.
The radio receiver 52 and its coupled receiving antenna 84 are
positioned atop the laser receiver 50, for purposes described
above. The laser and radio receivers 50 and 52, and, optionally,
the extension measuring device 82, are coupled to the portable
computer via a cable 86.
In order to determine the elevation at the location to be surveyed
or marked, an operator orients the receiver 14 vertically and
adjusts the extensible rod 80 until the datum laser beam strikes
the receiver 14 at a predetermined position, at which point the
extension of the extensible rod is determined by the extension
measuring device 82 and is entered into and recorded by the
computer 16. The elevation Z is, thus, equal to the height above
ground at which the datum laser beam intersects the receiver
14.
In the laser receiver 50 shown in FIG. 7, the predetermined
position at which the datum laser beam must strike for elevation
measurements is at the center 88 of a vertical array of
photodetectors 90. The photodetectors 90 are arranged in vertical
rows on the four sides of a support structure 92 within a
transparent casing 94. Each level of photodetectors 90 contains
four photodetectors that are connected in common to a circuit shown
in block form in FIG. 8. The four photodetectors 90 on each level
may be connected in common because the laser receiver 50 needs to
detect the heights and times at which the laser beams strike, but
not the orientations. The photodetectors located above the center
level of photodetectors 88 are coupled to a first detector circuit
96, while the photodetectors located below the center level of
photodetectors are coupled to a second detector circuit 98. The
center level of photodetectors 88 is coupled to a third detector
circuit 100.
The three detector circuits 96, 98, and 100 illuminate one of three
indicators 102, 104, or 106, respectively, depending upon which
photodetector 90 receives the datum laser beam. The indicators
102-106 are used to communicate with the operator during elevation
measurements. If the datum laser beam strikes any of the
photodetectors located above the center level 88, then the receiver
is positioned too low, in which case detector circuit 96
illuminates indicator 102 to inform the operator to raise the laser
receiver 50 by extending the extensible rod 80. The photodetectors
located above the center level may be subdivided into two groups, a
low-fine group 108 located close to the center level and a
low-coarse group 110 located toward the upper end of the array of
photodetectors. Such a grouping can be utilized advantageously to
inform the operator as to which group, fine or coarse, is receiving
the datum laser beam, so as to inform the operator how much to
adjust the height of the rod 80. The indicator 102 preferably glows
continuously when the low-coarse group 110 is struck by the datum
laser beam and glows intermittently when the low-fine group 108 is
struck.
Similarly, if the datum laser beam strikes any of the
photodetectors located below the center level 88, then the receiver
is positioned too high, in which case detector circuit 98
illuminates indicator 104 to inform the operator to lower the laser
receiver 50 by retracting the extensible rod 80. The photodetectors
located below the center level may be subdivided into two groups, a
high-fine group 112 located close to the center level and a
high-coarse group 114 located toward the lower end of the array of
photodetectors. The indicator 104 preferably glows continuously
when the high-coarse group 114 is struck by the datum laser beam
and glows intermittently when the high-fine group 112 is
struck.
Once the height of the receiver 14 has been correctly adjusted, the
datum laser beam will strike the center level of photodetectors 88,
which triggers the detector circuit 100 to illuminate the "on
datum" indicator 106. At this point, the height of the receiver is
determined in order to calculate the elevation at that location of
the receiver.
Since two, spaced-apart laser beams are received by the laser
receiver 50, means must be provided to distinguish between the two
laser beams so that only the datum laser beam will trigger the
on-datum indicator 106. Such means can recognize the datum laser
beam as the higher or lower of the two laser beams, as the case may
be.
The above-described receiver 14 is just one of many ways of
implementing an elevation detector responsive to a laser datum
plane. Another implementation will be described below in reference
to FIG. 19. Other elevation detectors can be found in the prior
art, including those disclosed in U.S. Pat. Nos. 3,469,919,
3,894,230, and 4,030,832.
The above description of elevation measurement assumes that the
datum plane is horizontal. If the datum plane is inclined, the
height measured at the receiver must be corrected for the tilt of
the datum plane in order to obtain a true elevation measurement.
This correction is simply a function of the measured planar
position of the receiver.
A timing circuit 116, shown in FIG. 9 and contained in the
interface circuit 56, is used to measure the time intervals needed
to compute the position of the receiver 14. The timing circuit 116
is seen to include three timers 118, 120, and 122. The portable
sensing station 13 includes two such timing circuits 116, one
coupled to one channel of the laser and radio receivers 50 and 52,
and the other coupled to the other channel of the laser and radio
receivers. Each timing circuit 116 supplies to the computer 16 a
value equal to a pair of time intervals, 70 and 72, or 74 and
76.
Interval timer 118 is used to determine the time interval between
the receipt of a radio signal and the detection of the
corresponding laser beam, namely time intervals 72 and 74, while
period timers 120 and 122 function alternately to determine the
period of rotation of the laser beam, namely time intervals 70 and
76. A signal from the radio receiver 52, a radio signal detect
signal, is supplied to the start terminal of interval timer 118 and
to the input port of a flip-flop 124. A signal from the laser
receiver 50, a laser detect signal, is supplied to the stop
terminal of timer 118, and is supplied through a delay line 130 to
the reset terminal of timer 118. One output terminal of the
flip-flop 124 is coupled to the start terminal of timer 120, the
stop terminal of timer 122, and the input terminal of a delay line
126. The other output terminal of the flip-flop 124 is coupled to
the stop terminal of timer 120, the start terminal of timer 122,
and the input terminal of another delay line 128. The output
terminal of delay line 126 is coupled to the reset terminal of
timer 122, while the output terminal of delay line 128 is coupled
to the reset terminal of timer 120. The data output terminals of
all three timers are coupled to the computer 16.
In operation, timer 118 starts measuring a time interval, either 72
or 74 upon the receipt of the radio (reference) signal detect
signal from the radio receiver 52. This signal also passes through
the flip-flop 124 and starts one of the other timers 120 or 122,
depending on the position of the flip-flop. Upon the subsequent
receipt of the laser detect signal, timer 118 stops timing and the
computer 116 reads the contents of the timer as a measure of time
interval 72 or 74. Once the computer has had enough time to read
the contents of the timer, the delay line 130 resets timer 118 to
prepare for the next measurement interval. Upon the next receipt of
the radio signal detect signal, the period timer 120 or 122 that
had been timing stops, and the other period timer 120 or 122 that
had been stopped starts, and the interval timer 118 also starts.
Two period timers 120 and 122 are utilized to measure the
rotational period of the laser in order to measure each period
while allowing the computer to read the measured value. Once timer
120 stops and timer 122 starts, the computer reads the value of
timer 120, and, shortly thereafter, the delay line 128 resets timer
120 so that it will be ready to time the next succeeding
period.
As an alternative, the timing circuit 116 could include two
interval timers, one of which measures the time interval between
the receipt of a radio detect signal and the receipt of a laser
detect signal, and the other of which measures the time interval
between the receipt of the laser detect signal and the next
succeeding radio detect signal.
In reference now to FIGS. 10 and 11, the operation of the
programmed computer 16 during computation of the position of the
receiver 14 will now be described. The first two steps, which may
be carried out serially or in parallel, involve the computation of
the two angles 58 and 60 that define the position of the receiver.
Angle 58, which is the angle measured clockwise from the reference
line 48 to the line 62 between reference station 38 and the
receiver 14, will be denoted as .phi..sub.A, while angle 60, which
is the angle measured clockwise from the reference line 48 to the
line 64 between reference station 42 and the receiver 14, will be
denoted as .phi..sub.B. To compute angle .phi..sub.A, the computer
reads the value of the interval timer 118 of channel A, reads the
value of the period timer 120 or 122 of channel A, and divides the
first value by the second value, where channel A is the timing
circuit 116 that responds to the detection of the laser beam
projected by reference station 38 and the reception of the radio
signal triggered by laser detector 44. Similarly, to compute angle
.phi..sub.B, the computer reads the value of the interval timer 118
of channel B, reads the value of the period timer 120 or 122 of
channel B, and divides the first value by the second value, where
channel B is the timing circuit 116 that responds to the detection
of the laser beam projected by reference station 42 and the
reception of the radio signal triggered by laser detector 40.
The next step in the operation of the programmed computer is to
determine the coordinate position of the receiver 14 in an XX-YY
coordinate system, wherein the XX axis extends in a positive
direction from reference station 38 (station A) through reference
station 42 (station B) and the YY axis extends orthogonally to the
XX axis beginning at reference station 38. The separation distance
between the two reference stations 38 and 42 is denoted as L. The
computer computes the XX,YY position of the receiver 14 according
to the following equations: ##EQU1##
In the next step, which may be eliminated if the position data is
to be expressed only in terms of XX-YY coordinates, the programmed
computer transforms the XX,YY coordinates into an X,Y coordinate
system, which may be a more useful way of expressing the
position-defining data. The XX axis is rotated an angle of
.phi..sub.C with respect to the X axis. The coordinate location of
reference station 38 is (X.sub.A,Y.sub.A), while the coordinate
location of reference station 42 is (X.sub.B,Y.sub.B). The computer
computes the X,Y position of the receiver 14 according to the
following equations: ##EQU2##
In the final step, the programmed computer stores the X,Y and/or
XX,YY coordinates as computed above, and also stores the measured
elevation or Z value for that location of the receiver 14. At this
point, the measured position and elevation can be corrected for any
inclination of the datum plane. The operator then places the
receiver 14 at another location to be surveyed or marked and
reinitiates the data gathering process described above.
The planar position of the receiver 14 can thus be computed in the
XX,YY coordinate system by knowing .phi..sub.A, .phi..sub.B, and L.
The planar position of the receiver 14 can be transformed into
another coordinate system by knowing the coordinates of one
reference station and the angle .phi..sub.C, or the coordinates of
both reference stations. Although not specifically discussed, the
above calculation can alternatively be carried out in or
transformed into an R,.THETA.,Z coordinate system.
When the reference stations 38 and 42 are initially set up, their
positions may not be known. If not, the following calibration
procedure may be utilized to determine the coordinates of the
reference stations knowing the X,Y coordinates of two bench mark
locations. As shown in FIG. 12, bench mark location #1 has the
known coordinates of (X.sub.1,Y.sub.1) in the X,Y coordinate
system, and bench mark location #2 has the known coordinates of
(X.sub.2,Y.sub.2) in the X,Y coordinate system. The coordinates of
the reference stations 38 and 42 in the X,Y coordinate system and
the separation distance therebetween need not be known prior to
calibration. The calibration procedure involves positioning the
receiver 14 at each bench mark location and determining the angular
position of each bench mark location with respect to the reference
stations. The position of bench mark location #1 relative to the
reference stations is given by (.phi..sub.A1,.phi..sub.B1), and the
position of bench mark location #2 relative to the reference
stations is given by (.phi..sub.A2,.phi..sub.B2), as shown in FIG.
12. Once the angular coordinate data has been obtained, the
following equations can be utilized to compute the coordinates of
the reference stations, the separation distance, and the angle
.phi..sub.C : ##EQU3##
Since the tangent function is undefined at angles of 90.degree. and
270.degree., the following equations apply when either .phi..sub.A
or .phi..sub.B are equal to one of those values:
When .phi..sub.A =90.degree. or 270.degree., G=0, H=Tan
.phi..sub.B
.phi..sub.B =90.degree. or 270.degree., G=1, H=-Tan .phi..sub.A
If the datum plane is inclined, then the inclination of the datum
plane can be obtained by measuring the elevations of three bench
marks and then finding the unique plane that passes through the
three bench marks.
The position sensing accuracy of the present invention is a
function of the location of the receiver 14 with respect to the
reference stations 38 and 42. Along the reference line 48, the
position of the receiver 14 can not be determined because both
angles 58 and 60 would be equal to zero and the triangle formed by
lines 48, 62, and 64 would collapse into a straight line. Even
apart from the region along or near the reference line, the
accuracy of position sensing utilizing the present invention is
effected by factors such as divergence of the laser beams,
uncertainty due to photodetector size, variations in the angular
velocity of the laser transmitters, and tolerances for measuring
time intervals and computing angles. Certain of these factors can
be corrected for by the computer once a first order determination
of position has been made.
In reference now to FIG. 13, there is shown an adaptation of the
previously described portable sensing station 13 that enables the
position sensing system of the present invention to be used for
position locating for purposes such as marking. In addition to the
receiver 14, interface 56, and computer 16, the portable sensing
station 144 further includes a location error indicator 146 and a
data base 148. The data base 148 is coupled to the computer 16 and
contains information that defines the positional coordinates of the
positions to be located. The location error indicator 146 is an
output device that informs the operator of the direction and,
preferably, also the magnitude of a positional error.
In operation, the operator instructs the computer 16 to retrieve
the positional coordinates of a selected location from the data
base 148. The operator then positions the receiver 14 at a trial
location and instructs the computer 16 to determine the position of
the receiver at that point. The computer then compares the measured
position of the receiver, as determined by the procedure described
above, with the desired position thereof, as specified by the
positional coordinates of the selected location retrieved from the
data base 148. The difference between the measured and desired
positions is a positional error that is communicated to the
operator through the location error indicator 146. The operator
then adjusts the position of the receiver 14 until the positional
error is substantially equal to zero. At that point, the receiver
14 is positioned at the selected location, and the operator can
plant a stake or other marker if necessary. The elevation at this
position can also be measured and compared to a desired elevation,
and any difference between the measured and desired elevations can
be noted. The desired elevation at the location to be marked can be
obtained from a site plan and stored in the data base 148, or can
be computed by interpolating between the desired elevations of two
adjacent elevation-defining line segments, according to an
interpolation method described below in conjunction with FIG. 23.
Once the marking or measuring tasks have been completed at that
location, the portable sensing station 144 can be used to find yet
another location to be marked.
Now that the apparatus and methods relating to the use of the
present invention in surveying and marking have been described, we
turn to the use of the present invention in grading implement
sensing and controlling. The major difference between the use of
the position sensing system of the present invention for grading
implement sensing and control and the previously described uses is
that the portable receiver 13 of the position sensing apparatus 10
is mounted on an earth-moving vehicle or other grading equipment,
and is used to assist the operator of the earth-moving vehicle in
grading the tract of land to a desired contour. The desired contour
is defined in terms of desired elevation (Z) of the graded tract
with respect to planar position (X,Y).
As shown in FIG. 14, an earth-moving vehicle 150 is equipped with a
blade or grading implement 152, the position of which with respect
to the vehicle 150 can be varied by hydraulic cylinders 154
according to means well known in the art. The apparatus of the
present invention, as applied to implement sensing and control, is
utilized to measure the elevation (Z) of the graded surface 156
with respect to a datum laser plane 158. The implement sensing and
control apparatus of the present invention is mounted to the
earth-moving vehicle and includes a laser receiver mast 160, a
remote processing unit 162, and an indicator 164. The laser
receiver mast 160 is coupled to the grading implement 152 for
movement therewith so that the mast elevation is directly related
to the elevation of the grading implement. In other words, the mast
160 is raised and lowered as the grading implement 152 is raised
and lowered. Means (not shown) may be utilized to keep the mast 160
in a vertical orientation regardless of the orientation of the
vehicle or implement. As shown in FIG. 15, the remote processing
unit 162 preferably contains a programmed computer 166 and coupled
data base 168, and a radio signal receiver 170. The radio signal
receiver 170, the laser receiver 160, and the indicator 164 are
coupled to the computer 166 through an interface 172 in a manner
similar to interface 56 described above. The indicator 164 is
mounted in or near the cab of the earth-moving vehicle and is
utilized to display to the operator of the earth-moving vehicle an
indication of the elevation error of the grading implement as
determined by the computer 166. When used to automatically control
the height or elevation of the grading implement 152, the apparatus
further includes an implement controller 174, which is coupled to
the computer 166 through the interface 172, and which is capable of
automatically adjusting the position of the grading implement in
order to reduce the elevation error, as described below.
The laser receiver mast 160, like the laser receiver 50 of receiver
14 described above, is operable for detecting when each laser beam
strikes the mast, and is also operable for detecting the height at
which one of the laser beams, the datum laser beam, strikes the
mast. Instead of providing an extensible support structure to
elevate the laser receiver to the proper height, an alternative
construction having a fixed height, illustrated in FIG. 17, is
preferably employed for the laser receiver mast 160. The laser
receiver mast 160 preferably includes an elongated linear array of
photodetectors 176, extending vertically for a distance of several
feet. The photodetectors 176 are arranged in four vertical rows of
a support structure 178 within a transparent casing 180. Each level
of photodetectors is preferably coupled in common to the interface
circuit 172. The array of photodetectors is preferably disposed
above the roof of the earth-moving vehicle so that the laser beams
may be received at any orientation of the vehicle. The elevation
measurement of the grading implement 152 is determined from the
height at which the datum laser beam strikes the laser receiver
mast 160, as detected by whichever of the photodetectors 176 the
datum laser beam strikes. Unlike receiver 14, the height of the
mast 160 is not adjusted for purposes of making the elevation
measurement, thus speeding up the measurement process.
In operation as an implement sensing apparatus, the laser receiver
160, the radio receiver 170, the interface 172, and the programmed
computer 166 operate as described above in sensing the position of
the laser receiver in the plane of the laser beams. The planar
position of the laser receiver 160 is determined by the
triangulation technique described above in conjunction with the
surveying and marking apparatus. In other words, the two angles,
.phi..sub.A and .phi..sub.B, are calculated according to the ratio
of the time intervals defined by the receipt of the radio signals
and detection of the laser beams, and are, optionally, converted
into XX-YY, X-Y, or other coordinate systems. The measured
elevation of the grading implement 152 is determined according to
the height at which the datum laser beam strikes the laser receiver
mast 160. Using the measured planar position, the computer
determines a desired elevation of the grading implement 152, where
the desired elevation can be retrieved from the data base 168 or
interpolated from elevation-defining data stored therein. The
difference between the desired and measured elevations of the
grading implement 152 is an elevation error thereof, and is
displayed to the operator of the earth-moving vehicle 150 using the
error indicator 164. By knowing the magnitude and direction of the
elevation error, the operator of the earth-moving vehicle can
adjust the position of the grading implement so as to reduce or
eliminate the elevation error so that the vehicle will grade the
site to the desired elevation. Since the implement sensing
apparatus continually recomputes the planar position of the laser
receiver, the desired elevation need not be a fixed distance from
the datum plane 158, but, rather, can vary according to the planar
position.
In operation as an implement control apparatus, the implement
controller 174 is utilized to automatically control the height of
the grading implement 152 as a function of the planar position of
the laser receiver 160. The implement control apparatus operates
like the implement sensing apparatus in computing an elevation
error of the grading implement as a function of the planar position
of the laser receiver 160 and vehicle 150, but adds the step of
automatically adjusting the height of the grading implement in
order to reduce the elevation error thereof. The implement
controller 174 is preferably a hydraulic control device that, in
response to an elevation error signal, causes the hydraulic
cylinders 154 to vary the height of the grading implement in such a
way as to reduce or eliminate the elevation error. If the elevation
error is of great magnitude, which may occur if a large cut or fill
is required at that vehicle position, the capabilities of the
earth-moving vehicle may dictate that several grading passes will
be required to produce the desired graded surface. In such a case,
the controller 174 would reposition the grading implement 152 for
that particular grading pass at a position that reduces but does
not totally eliminate the elevation error.
In addition to sensing and/or automatically controlling the
elevation of the grading implement, it may be advantageous to also
sense and/or control the lateral position of the grading implement.
As shown in FIG. 17, the earth-moving vehicle 150 is grading to a
desired lateral contour 182. The contour 182, which may, for
example, represent the edge of a road, is defined within the data
base. In order to produce the desired contour 182, the right edge
184 of the grading implement 152 must follow the contour.
Accordingly, the computer includes means for determining the
lateral position of the right edge 184 of the grading implement
based on the measured position of the earth-moving vehicle and
grading implement and for computing a desired lateral position
thereof based on the data base representation of the desired
contour 182. A lateral positioning error is computed as the
difference between the actual and desired lateral position of the
grading implement. The lateral positioning error can be displayed
to the operator on the error indicator 164 and/or can be used by
the implement controller 174 to automatically adjust the lateral
position of the grading implement so that the desired lateral
contour is produced. Additionally, the control system may include a
vehicle steering controller 186 (FIG. 15) that automatically steers
the earth-moving vehicle along the desired lateral contour.
In the above discussion of the implement sensing and control
apparatus and method, it has been assumed that only the elevation
or lateral position of the grading implement 152 needs to be
controlled in order to produce the desired graded surface. While
this may be true in certain cases, such as grading a flat surface
or when using earth-moving vehicles such as bulldozers or trenching
machines, more generally, this assumption is not correct. Since the
desired graded surface is often inclined, the grading implement may
necessarily be sloped in order to produce the desired graded
surface.
For example, if the desired graded surface is a constant-slope
incline and if the grading implement is disposed at right angles to
the direction of travel of the earth-moving vehicle, then the
grading implement will be horizontal only if the vehicle is moving
directly up or down the fall-line of the incline. If the vehicle is
moving at right angles to the fall-line of the incline, then the
desired slope of the grading implement is equal to the angle of the
incline. If the grading implement is oriented in any other
direction, then the desired slope of the grading implement will be
some intermediate value between the angle of the incline and
horizontal. Thus, in general, the desired attitude of the grading
implement is a function not only of the planar position, but also
of the orientation of the grading implement.
In order to deal with the general situation wherein both the planar
position and orientation of the grading implement effects the
desired attitude thereof, the implement sensing and control
apparatus and method preferably includes means for measuring both
the planar position and orientation of the grading implement, and
also includes means for determining the desired elevation and slope
of the grading implement as a function of the measured position and
orientation thereof.
One approach is to determine elevation errors at both ends of the
grading implement 152 by utilizing two laser receiver masts 160,
each coupled to opposite ends of the grading implement, as shown in
FIG. 18. In this embodiment, the remote processing unit 162 would
include two channels of processing, one operable for determining
the planar position and elevation of the left mast 188, and the
other operable for determining the planar position and elevation of
the right mast 190. The planar position of the left mast would be
determined according to the measured angles .phi..sub.AL and
.phi..sub.BL, while the planar position of the right mast would be
determined according to the measured angles .phi..sub.AR and
.phi..sub.BR, as shown in FIG. 19. The elevation of the left side
of the grading implement 152 would be determined according to the
height at which the datum laser beam strikes the left mast 188,
while the elevation of the right side of the grading implement
would be determined according to the height at which the datum
laser beam strikes the right mast 190. Once the planar position and
measured elevation for each end of the grading implement are
determined, the desired elevation at each end can be found from the
elevation-defining data stored in the data base 168, and an
elevation error for each end of the grading implement can be
computed. The error indicator 164 or the implement controller 174,
in this embodiment, includes two channels to respectively indicate
or correct for the two elevation errors.
An alternative approach is shown in FIG. 20 wherein a single laser
receiver mast 160 and associated single channel remote processing
unit 162 are utilized, as described above, to determine the planar
position and elevation of the grading implement. In this
embodiment, the remote processing unit 162 additionally includes an
implement orientation sensor 180 (FIG. 15) that senses the
orientation of the grading implement with respect to a datum
direction, such as north, and senses the slope of the grading
implement with respect to another datum such as a horizontal plane.
Knowing the orientation of the grading implement plus the planar
position and elevation thereof, the computer 166 can determine a
desired slope of the grading implement. By subtracting the measured
slope from the desired slope thereof, a implement slope error can
be found. The implement slope error can be displayed on the
indicator 164 along with the elevation error, and/or can be
utilized by the implement controller 174 to automatically adjust
the slope of the implement to reduce the slope error.
FIGS. 21-24 illustrate the processes of surveying and marking a
plot of land 200 utilizing various aspects of the present
invention, and of developing a contour map, a site plan, and a
cut-fill map, from the information obtained from surveying. FIG. 21
shows the plot of land 200 in its natural state, falling downward
into a dip 202 from the edge of a road 204, and then rising upward
toward the crest of a hill 206. In order to survey the plot of land
200, two reference stations 208 and 210 are set up across the road
with their laser beams sweeping across an area that includes the
plot of land and the opposite reference station. The reference
stations are positioned at known locations, known with reference to
two bench mark locations through the use of the calibration
technique described above.
The surveying process, according to the present invention, involves
sequentially placing the portable receiver 212 at various locations
214 throughout the plot of land 200, and at each location measuring
the planar position of the receiver with respect to the reference
stations and measuring the elevation of the receiver with respect
to the datum laser beam. Once the reference stations have been set
up and calibrated, the data gathering portion of the surveying
process is a one-person job, assuming only one receiver 212 is
used. Of course more than one receiver 212 and associated operator
could be utilized to speed up the data gathering process.
Preferably, the receiver 212 is sequentially positioned at various
locations 214 along the bottom of the dip 202, along the crest of
the hill 206, and at enough positions throughout the plot of land
and just outside the boundaries thereof to adequately cover the
plot of land. The locations 214 are preferably selected so that the
ground along the line segments 215 that connect the locations 214
is straight, i.e., has a constant slope, either zero or non-zero. A
suggested pattern of survey locations is shown in FIG. 22. The
measured planar position and elevation of each location is stored
in the portable computer for later use.
Once the entire site has been covered by the data gathering
process, the data obtained can be reduced to a more visually useful
form by creating a contour map that includes constant elevation
lines 216. The process of determining the locations of the selected
constant elevation lines involves interpolating between adjacent
survey points whose elevations span the elevation of the line. For
example, to compute points 218 and 220 along the fifty-two foot
elevation line, one would first locate survey points whose
elevations are close to fifty-two feet. Points 222, 224, and 226
satisfy that condition. One would then linearly interpolate between
two points, such as 222 and 226 or 224 and 226, to determine where
on the straight line therebetween the elevation is equal to
fifty-two feet. The same steps are followed to find additional
points along the rest of the constant elevation lines. The lines
between points 222 and 228 and 224 and 228 define two points, 230
and 232, along the fifty foot elevation line. Once all the
interpolation has been done, the constant elevation lines are
generated by simply connecting the points.
The data obtained through the surveying process can also be used
for generating a site plan and for estimating the elevations at
various key locations on the site plan. As shown in FIG. 22, if it
is desired to grade the plot of land 200 into a rectangular parking
lot 234, the elevations at the corners of the lot may be useful to
know. In such case, an interpolation routine using two nearby line
segments 237 and 239 can be used to estimate the elevation of
corner 242. The interpolation involves first defining a straight
line 244 that passes through the corner of the lot at point 242 and
through one or both line segments. The line 244 may pass through
one end point and one line segment 237, as shown, or may pass
through both line segments. The elevation at point 246 is
determined by linear interpolation between the two end points 236
and 240 of line segment 237, the elevations of which are known from
the survey operation. The elevation at point 242 is then determined
by linear interpolation between the elevations at points 238 and
246.
A site plan, as shown in FIG. 23, defines the desired graded
surface in terms of planar positions and elevations of several key
locations, such as corners 242, 248, 250, and 252 and drain 254.
According to the present invention, the desired elevations of
points along the connecting line segments between those key
locations are found by linear interpolation between the elevations
of the end points of the lines, while points interior of the
connecting line segments are determined as if the triangular space
between three connecting line segments defines a plane. To find the
desired elevation of a point 256 within the triangle defined by
points 242, 248 and 254, a line 258 is drawn through the point 256
and through the two sides of the triangle. The elevation at each
intersection of the line 258 and the triangle is determined by
linear interpolation. For instance, in the illustrated example, the
desired elevation at point 260 is equal to 50.0 feet, because the
entire line between points 242 to 248 has a desired elevation of
50.0 feet. Also, the desired elevation at point 262 is 48.7 feet,
based on a linear interpolation between the 50.0 foot desired
elevation at point 242 and the 48.0 foot desired elevation at point
254. The desired elevation at point 256 is then found to be 49.5,
based on a linear interpolation between the 50.0 foot desired
elevation at point 260 and the 48.7 foot desired elevation at 262.
Alternatively, another line 264 could be used to find the desired
elevation at point 252, but the result should be the same. Also
alternatively, a line (not shown) could be drawn through point 256
and one of the vertices 242, 248 or 254 of the triangle, and the
elevation at point 256 would be determined by linear interpolation
between the desired elevation of the vertex and the elevation at
the intersection of the line and a side of the triangle. Thus, the
site plan is defined according to the desired elevations of the end
points of the line segments and the desired elevation at any point
within the site plan can be calculated by interpolation between
nearby line segments.
This technique for determining the desired elevation at a point
based on the elevations for adjacent points can also be used,
according to the present invention, in determining cut and fill
information while marking, or in determining elevation errors
during implement sensing or control with the present invention.
Once the site plan has been defined and the site has been surveyed,
a cut-fill map can be calculated, as shown in FIG. 24. The
pre-existing land elevations within and along the boundaries of the
site plan can either be estimated from the survey data, as
described above, or may be remeasured through a marking procedure.
The marking procedure would involve defining those locations where
an elevation measurement is desired, positioning the receiver 212
and measuring the elevation at each of those locations. Knowing the
desired and actual elevations of the land, the cut-fill map is
calculated by simply subtracting the two sets of values. For
example, the desired elevation of corner 242 of the parking lot is
50.0 feet, while the estimated elevation is 51.3 feet. The
difference, 1.3 feet is the depth of cut that will be required at
that point to create the desired 50 foot elevation. The cut-fill
map is useful for estimating the job and for planning the task of
grading.
Having thus described the preferred embodiments of the present
invention, a number of alternative embodiments deserve mention. As
shown in FIGS. 25 and 26, a portable sensing station 270 or a
reference station 272 can be mounted in vehicles 274 or 276 for
ease of transportation and to speed up the process of obtaining
data with the present invention. A vehicle-mounted portable sensing
station 270 can speed up the surveying or marking process by
reducing the time to transport the portable sensing station between
locations to be surveyed or marked.
In FIG. 27, three reference stations 278, 280, and 282 can be used
simultaneously to improve the area of coverage and accuracy of the
present invention. In the regions 284, 286, and 288 near the
connecting lines between reference stations, the position sensing
accuracy of that pair of two reference stations is poor. However,
the other two pairs of reference stations can accurately determine
positions in those regions. In areas near each reference station,
the other pair of reference stations can be used to accurately
determine position. In all other regions, all three pairs of
reference stations can be used to measure position. In regions
where more than one pair of reference stations can be used for
position sensing, position sensing accuracy can be improved by
averaging the results of the position sensed by each pair. In order
for the position sensing system to know which pair or pairs of
reference stations to use, a provisional position can be determined
and used to select the pair or pairs of reference stations to be
used to determine the recorded position.
In FIG. 28, an alternative is shown to the above-described mounting
of the laser detectors 20 and radio signal transmitters 22 on the
reference stations. In this alternative embodiment, the laser
detectors and radio signal transmitters are positioned at point
290, which is intermediate to the locations of the two laser
transmitters 292 and 294. If point 290 lies on the line 296
extending between the two laser transmitters, then the line 296 is
the reference line for purposes of defining both angles 298 and
300. If not, each line segment 302 and 304 functions as a separate
reference line. The position of the receiver 306 can be determined
with respect to the laser transmitters 292 and 294 and the
non-coincident reference lines 302 and 304, although the
mathematics involved is more complex than disclosed above for the
case where the two reference lines are coincident. The locations of
the laser transmitters 292 and 294 and the two reference lines 302
and 304 can be determined through a calibration procedure using
three bench mark locations.
The depth of disclosure herein, while lacking great detail in the
specific design of individual components of the present invention,
is sufficient for one of ordinary skill to construct the present
invention. It is well known in the art to construct laser
transmitters and detectors, radio transmitters and receivers,
hydraulic controllers, error indicators, programmed computers,
electronic interfaces, data bases, and other apparatus that will
accomplish the functions of the present invention as set forth
herein.
From the above description, it will be apparent that the invention
disclosed herein provides a novel and advantageous
three-dimensional position sensing apparatus and method utilizing
laser reference stations and one or more portable position sensors.
The foregoing discussion discloses and describes merely exemplary
methods and embodiments of the present invention. As will be
understood by those familiar with the art, the invention may be
embodied in other specific forms without departing from the spirit
or essential characteristics thereof. For example, the laser beams
could be projected on the same plane and the radio signals could be
broadcast at the same frequencies, but the portable sensing station
could still distinguish between the two laser beams and radio
signals if the period of the two lasers are different. Also, the
three timer circuit 116 could be constructed in many different
alternative ways with the same or a different number of timers.
Also, the definition of location in terms of angles and the
formulas for calculating position or transforming position data to
other coordinate systems could be modified. Also, certain portions
of the portable sensing station, such as the computer, could be
located at a distance from but electrically coupled to the
receiver. Multiple receivers can be used and coupled either to
separate computers or to a central computer. Also, the laser beams
need not rotate at constant angular velocities because the computer
could compensate for any perturbations in the angular velocities of
the laser beams during its timing and angle calculations. As
mentioned above, non-horizontal datum planes may be used.
Accordingly, the disclosure of the present invention is intended to
be illustrative, but not limiting, of the scope of the invention,
which is set forth in the following claims.
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